Pref shares do get diluted, they are however senior to common stock so they get money FIRST if there’s not enough to go around. There is some cap on this and sometimes it’s pretty high. Huge pref overhangs are, indeed, a problem.

Pref shares with a 1x preference are still worth like 10x common stock in early stage companies and it’s common for employed to get fucked by this.

Founders don’t get preferred shares (I think it’s really, really rare). There is founder pref stock, which is somewhat different. It’s common for founders to cash out some shares along the way, though.