I think he has glowlight tetras as opposed to glowfish. Glowlights are nice and small and school well, so I'd definitely at least double what you have but more is even better. A dozen would probably put on a nice display. With 4 feet of length you could probably do another school and since it sounds as if you're looking for sort of an amazon themed tank, add another school of medium sized tetras, plus 6-8 cories on the bottom and a couple of bristlenose plecos
As for the angels, there is a possibility they will grow large enough to have a tetra for lunch, so you will need to get larger tetras or go with a bit less aggressive centerpiece fish. Also, you will need stay away from nippy fish as they will go after the angels.
Bolivian rams might work as a centerpiece but they could still be a bit aggressive towards smaller fish.
You could as was previously stated go with some flashy platys or mollies as a centerpiece as well. Platys are pretty active fish and a group of 3-5 would make a nice, active display.