I've played Imperial Guard in Kill Team. They are rather generic in the Core Manual. The KT: Elites book adds in sub-faction rules which for Guard mean unique regiment rules. These rules are very minor and tend to give each regiment one or two extra abilities or bonuses. I should note that Death Korps of Krieg don't yet have their own sub-faction rules in Kill Team. I'm not sure what your experience might be with DKOK in Kill Team. The Death Korps has many unique units and rules, they are much different than your run of the mill Guard regiment. Hopefully, you won't mind using the standard rules to represent DKOK in Kill Team. I think that the Valhallan sub-faction, which makes them much more resistant to moral effects, is a good sub-faction to approximate the Death Korps.
Well, the tournament community see Astra Militarum in Kill Team as basically a way to overwhelm your opponent with plasma guns (referred to as "Plasma Spam").
In general, AM can take upto 4 gunners (1 from the regular infantry squad and 3 from the special weapons squad), as well as upto 4 Scion gunners. So, if you wanted to spend your points on nothing but plasma guns, then you could get upto 8 plasma guns (or an assortment of whatever special weapons you want). You can mix and match regular guardsmen and scions in your kill team. Thematically, I prefer having either a complete guardsmen kill team or a complete scion kill team. Also, Astra Militarum in Kill Team presently cannot get heavy weapons. This is no doubt because imperial guard heavy weapons are currently mounted on giant 60mm bases which would not work in Kill Team.
Here are some thoughts on Astra Militarum special weapon choices:
Flamer: A great weapon in Kill Team. Your flamer equipped miniature can make an Advance Move and then fire an assault weapon at -1 to hit. However, the Flamer automatically hits its target(s) so you are left with a weapon that has a big threat range/radius, yet still functions at full capacity. Also, the Flamer is a great weapon for using in overwatch. Defensively, I often try to make my forward Flamer model the only model within charge range of my opponent. So if they want to charge my force, hopefully they will be taking up to D6 automatic Flamer hits. Flamers are your go to weapon for fighting horde factions. And remember, you can split fire with a flamer just like any other ranged weapon with multiple shots. Lastly, regular guardsmen have a modest BS of 4+ which isn't great, but since the Flamer always hits its target, it is always a solid choice. Conversely, Scions have a BS of 3+, making them good shots, and I am loathe to equip any scions with Flamers.
Grenade Launcher: The gotta win competitive players would never recommend the humble Grenade Launcher. However, I have a soft spot in my heart of the somewhat mediocre Grenade Launcher. It has a range of 24 and two different ammo types. The frag grenade is like the frag grenades or frag grenade equivalents that most armies get. Handy, against horde forces, not as certain as a Flamer, but you have much better range. The krak grenade is the second ammo option, it has a high strength, but its AP is only -1. The Grenade Launcher is similar to the Missile Launcher, it is flexible, but not great at either of its two options. I'm working on a Penal Legion themed kill team. I won't have any scions and I plan to take 4 Grenade Launchers. I imagine that the prison guards or Arbites guarding the prisoners all carry Grenade Launchers to either gas or frag any prisoner riots or uprising.
Plasma Gun: Widely considered the best Astra Militarum special weapon. It has good range, a great AP, and a high strength. When overcharging the Plasma Gun causes 2 Dmg, which given how injury rolls are calculated in Kill Team is highly desirable. Guard can take the Sniper specialism which is pretty much the go to combo for any Plasma Gun. Sniper's can reroll 1s on to hit rolls, making a Plasma Gun killing the owner very low. I consider Guard kill teams with too many Plasma Guns, over used and playing on easy mode. I always like the idea of a Guard kill team operating like the old Colonel Scheafer's Last Chancers. You have one expert at each of the special weapons that the squad carries. They have Scope, obviously a Sniper specialist with Sniper Rifle. They have Ox, a big burly guardsman who carries a Heavy Bolter all by himself, definitely a Heavy specialist. The have Hero, a natural leader who of course would be a Leader specialist. They have Rocket Girl, she carries a Missile Launcher and would be well represented as a either a Heavy specialist, a Sniper specialist, or even a Veteran specialist. Anyway, a variety of special weapons is the way to go in my mind. I try to design missions for the other players in my little gaming group, and I'm always keen to reward kill teams with a variety of weapons/options as opposed to the boring Plasma Spam that many players consider mandatory.
Meltagun: This weapon is the most powerful thing in the Astra Militarum arsenal for Kill Team. It does have a very short range, though in games of Kill Team that isn't automatically a deal breaker. A Heavy specialist armed with a Meltagun can advance and shoot his Meltagun without a -1 to hit. The big drawback to the Meltagun is that the Plasma Gun is just a little worse stat-wise, but has a much longer range and two shots within half range. Also, a regular guardsman with a BS of 4+ is going to miss a lot with a Meltagun, which makes him less than effective and means he will often be rushing into short range, but not eliminating a potentially very threatening enemy model who will then retaliate. A scion with a Meltagun is a much better choice. He hits more often and his better armor means that he might just survive any enemy retaliations.
Sniper Rifle: Another weapon that many would never consider taking. But I mean c'mon, it's a Sniper Rifle. If your kill team is going to plant explosives in an enemy airstrip you want a damned Sniper Rifle for eliminating enemy sentries. Similarly, assaulting any fortified enemy position will almost always benefit from a Sniper Rifle. The Sniper Rifle has a range of 36" and it does not suffer the normal -1 to hit at over half range. On a 6 the Sniper Rifle can cause a mortal wound, which is random, but great when it happens. As a Heavy weapon the Sniper Rifle will suffer a to hit penalty if you move and shoot with it. You could equip a Heavy specialist with a Sniper Rifle, but Heavy specialists are much more valuable else where. The Sniper Rifle has no AP modifier, so it is often a disappointing weapon when fighting any one of the many well-armored factions in Kill Team. Also, only BS 4+ guardsmen can take Sniper Rifles, so you are once again putting your faith in a model with not-so-great aim. Scions cannot take Sniper Rifles, such a stand off weapon goes against the shock trooper role of scions.
Hot-shot Volley Gun: The scions lack Sniper Rifles, but in their place the scions get the Hot-shot Volley Gun. This weapon is unique to the scions, it is Heavy 4 and has a respectable range of 24" (respectable for Kill Team anyway). It is strength 4 and -2 AP. Meaning the Hot-shot Volley Gun packs a punch and is a threat to power armored Astartes and Heretic Astartes. Personally, I feel that the Hot-shot Volley Gun, in the hands of a Scion trooper, is approximately equivalent to the Plasma Gun. I would maybe take one of each or even two of each in a scion-only team. The high number of shots for the Hot-shot Volley Gun worth noting. If a tactic, ability, or Comms specialist gives a model with a volley-gun a bonus to hit (rerolling 1s or +1 to hit) it is much more effective on a weapon that can use the bonus on 4 shots (5 shots with the More Bullets, Heavy specialist level 1 tactic). At the end of the day, the Hot-shot Volley Gun is unique to guard/scions and can be a threat to both heavy infantry and hordes. If you are taking a kill team of all-scions, then I think you should bring at least one of this rarely seen weapon.
Vox-Caster: The Vox-Caster allows ALL models in an Astra Militarum kill team to reroll Nerve tests if the model carry it isn't Shake and is on the board. This is a tremendous benefit for imperial guardsmen. It is worth taking in a every kill team, if you combine guardsmen and scions you could even have two Vox-Casters for redundancy. Also, the Vox-Caster equipped miniature presents a great opportunity for miniature conversions. You can take a normal Vox-Caster bit and add extra antennas, loops, or dials. Will your Comms specialist wear a helmet or headset with his ear piece and microphone or will he have an old school handset connected to his Vox-Caster by a cord? Any extra high-tech bits and bobs that you want to include in your kill team will look great on your Vox-Caster equipped Comms specialist.
Wow. I didn't intend to write a full article! Well, I hope this is helpful. It would probably be worthwhile to review the different Astra Militarum regimental sub-factions in KT: Elites (or Battlescribe) before you plan out and begin gluing your guardsmen together. Also, be sure to use your full Command Roster when planning your kill team, it allows you to have much greater tactical flexibility and weapon options.