The tank sizes your looking at are too small for most tangs. Tangs are big, dirty fish, that create a lot of waste. They also need a lot of running room. You might get away with a yellow tang in a 350, but even that is pushing things a bit. No matter what, don't add more than a single tang to a systems of these sizes.
Humu Humu Trigger is not a good choice. First off they will eat any shrimp, crabs, snails and just about anything else in the invert area. They also grow fast, and as they mature they tend to kill off any fish they don't like. They aren't quite as bad as some triggers, but many can will turn your tank into a system housing just the trigger.
A copperband can be an ok fish, but make sure it's eating before you take it home. Also make sure it's not going to get bullied by other fish.
The spotted toby, a type of puffer, will also eat most inverts in the system. Add with caution.