The government within the book and movie is within the limits of liberal theory, militaristic, but liberal. It is meritocratic as civilians must earn their citizenship and have a right to choose not to, and it is a limited democracy in the same vein; not all choose to partake.
The SS uniform is purely from the movie and is purposefully chosen. Sargon of Akkad makes his position pretty clear in the video linked, if you’d bother to watch it; “You love Starship Troopers because you think that when the fascists come, and you are called upon, you will pick up a rifle and do your duty like you know you should… Nowhere in the world at any point in history has man lived lives of such tranquility, abundance, and freedom than under a liberal democracy.”
How you get fascist from those sentiments is beyond me.
Yep, Mumble is the most common, and there are still a couple groups that use Teamspeak.
Discord caps at 100 people in a call while I’ve seen good Mumble servers handle over 800.