I'd say no, just for the fact that bettas have long fins, but I've seen people have bettas and angelfish together no problem. I've always thought of angelfish to get nippy.
About keeping labyrinth fish together- It all depends on your tank and fish. I have a 30g tank with two dwarf gouramis (male and female, although the female is more aggressive than the male), and two paradise fish of an uncertain gender(they are still young). All get along fine, just a little chasing every now and again, but nothing too aggresive. No nipping, no fighting, nothing. I have them now crammed into a 10g hex with a lot less room (due to some tank problems) and they still get along great! So I don't think they ALL can't get along. There are cases of them getting along and some of them not.