There are quite a few questions in there!
What is your favorite set of rules for WW2 squad level gaming? NUTS!
What is your most liked set of rules for WW2 squad level gaming? 5Men in Normandy as the mechanics are so cool.
What is your most played set of rules for WW2 squad level gaming? My own, based on NUTS! but with less dice rolling.
If you play WW2 both with single-based and team-based figures (f.x. Nuts and Command Decision) do you do so in different scales or the same? I do squad in 20mm and team based in both 20mm (preferred) and 6mm (more so at the moment).
Is squad-level gaming the primary type of WW2 game for you or is it a secondary/occasional thing? Squad level is a very occasional thing. It has also been fairly recent. After starting gaming WW2 in 1980, I only played my first squad game in about 2012.