its a start. Welcome to SD first of all and I am saying that on behalf of the moderator team. your plan sounds reasonable, but I think you should consider purchasing a larger tank. The 90gal is an oddly sized footprint FME. Its the same with and depth as a 75 but its taller, too tall. Unless you are a person of incredible height, you will need a stool to be able to reach the substrate with your siphon hose during water changes. Secondly, angles are similar to discus in that they are a shoaling fish so 3 angels will bicker amongst themselves to the point of someone being stressed to death. for a mix of the two I would go with the minimum of a 6' footprint (125gal or more)