First of all, I would like to say that I can't go to events and don't have a lot of gaming experience and that the following can only be my own opinion.
What a fighter represents is decided with us by the profile card! - As a small group and in private among ourselves, we deal with it in such a way that the main armament and its category should be visible and recognizable. For example, whether a fighter has a melee weapon, pistol, rifle, a special or a heavy weapon. But grenades can also only be used as deco. In addition, before the start, we briefly introduce ourselves to each individual fighter and their profile. And if you want, you can also exchange your gang sheets.
But in many cases, Wysiwyg also depends on the event organizer, or the group, or maybe an arbitrator or unknown players. If nothing is given, I would therefore always ask beforehand. And when you're at it, I would also ask how and what is being played? - Easy going or Min-max, competition or narration?
In very less cases I have provided for a magnetization of the arms or weapons so that I have one or two miniatures in the gang, which I can weakly armed recruit cheaply and later change or improve them. For example two subjugators of the Palanite Enforcer. With or without shield, with baton or grenade launcher. But my other miniatures will not be converted after completion!
For Van Saar I don't know, especially since there is also the second box and the Forgeworld Champions, but for some gangs, sooner or later you should have a third sprue or a second gang box anyway. If real Wysiwyg is required or expected in an external campaign and I had no suitable alternative ready, I would always prefer to build a new miniature instead of converting a fully painted model.