Hello! Yeah, a 75g tank can indeed make an awesome angel set-up.
If you want multiple angels, I suggest lots of plants and stuff to break up the line of sight. If you want a breeding pair, then I suggest you start with a group of juveniles and let them grow a bit and pair off, then you re-home any stragglers or any fish that get particularly aggressive or what-not.
For tankmates, I suggest corys of some sort. They are fun, active, cute, and mind their own business on the bottom of the tank. There are a whole handful of pleco species that would do well in a 75g tank, just remember to stay away form the common pleco because it gets huge and messy.
As far as a school of fish. I personally suggest fish that are either spade-shaped or else at least 2 inches if they are torpedoe shaped, but thats just my rule, its not an absolute. It helps make sure they are too big to be eaten someday.
Cardinal tetras, black neons, and rummy-nose tetras are particular favorites of mine. I also live silver-tipped tetras and platys or mollies.
Honestly, you have all sorts of options. Happy stocking!