so you first question was how many fish can you fit. You seem to like goldies but I have to say I think they're a poor choice for a hex. Those kinda of tanks are hard because most fish like to swim horizontally more than vertically. I would say 1 big angel would look great in it, then a school of like 8-10 tetras. Something medium...not so small to get eaten and not so big that the tank feels cramped to them. Then have fun on the bottom with a pair of rams or something like that. a small group of cories would work too.
I wanted to try with things like the Orandas, Ranchu, Lionhead, Black Moor and maybe a Ryukin. I really do like fancy goldies, I really wanted a koi pond but just don't have the room for one.