They do. I mean my 350 is 60+ cm height inclusive of substrate and about 120cm length ways. I do get some aggression when they pair up, but they lay and the eggs get eaten as the tank isnt suitable for a breeding set up. I chose it this way and filled in with rainbow emperors so when the angels get bigger they wont become food.
I wouldn't over think it. As long as you keep on top of the cleaning and watch your feeding regime etc. I would say its ok to keep a pair of discus or angels in the tank no problem.
I do run 2 x jbl filters. Before I had e1500 which equated to (apparently) 2800lph filtration. That died over time and now I have 2 x e902 filters which is 1800 lph filtration.
Having adequate filtration is important and whilst mine was overkill as originally the tank was set up for a bunch of discus who furiously loved eaten beefheart. The tank itself has a double function as a planted tank which aids alot to the fish and cycling.
Rams are cool fish and yes rainbows can become bigger, but again as long as the filtration, cleaning and feeding regime is good you will have a happy tank for many years. You over time will work out whats best. In terms of maintaining, stocking levels, lighting, plants etc. Each tank set up is different.