I've had betta sororities in a 20 gallon and a 55 gallon. As already stated, every betta is different! Some are very laid back and don't bother anyone, and some are little terrors. I've had everything in between too. The bigger the tank, the more chance you'll have of your bettas co-existing peacefully. I had better luck in my 55 than my 20, obviously. More places to get away or hide. It's a crap shoot. I had to take a couple back to the store that were little hellions. But most of them did get along pretty well in the 55.
In a 30 gallon, you probably won't have very good luck, to be honest, unless you get super laid back ones. 4 angels in a 30, by the way, is way too much! For 4 angelfish, I would have them in nothing smaller than a 55. Sell your 30, get a 55, and then I guarantee you'll do a lot better with angels and bettas.