The royal and clowns should probably be in something more like a 20-25. I'm not saying it hasn't been done, just saying what is recommended.
But honestly, you bring up a good point. You will find out real quick that coral is where it's at. I would take coral over fish any day. And coral can be housed in any size tank as long as you keep the water consistent.
You should google ricordea mushrooms, different types of zoas, and LPS
in general. That might influence how you want to set up your tank.