I personally wouldn't add a tang, copperband, or a flame angel/coral beauty. I would add only one of them size they require a lot of space when they get older so instead of buying small and selling later I'd rather just buy one and keep it as long as possible. Just my two cents
Copperbands can be difficult. The clowns, Tang and Angel will probably stress it out and/or make eating difficult. The Regal will get way too big, so that will be short lived in a 50.