What I recommend is searching "75 fowlr stock" and see what other people are putting in their tanks for some inspiration and so you also know the limits of your tank. Saltwater is not like freshwater with the "inch per gallon" (even though that doesn't even really work with fresh either) you need to take into account the swimming territory of each type of fish, and their individual temperments.
The regals and the longnose butterfly are 125+ gallon.... I really think this one is a bad idea. What is your goal? Color? Activity? You change up your list so frequently and randomly that I can't track what your goal is.
I hope that you understand that it's not all about gallons. It also has to do with the tank dimensions. For example- I have a 65 gallon tank. A tomini tang can "technically" fit into my tank. However it is only a 3 foot tank (.9 m). A tang of any sort should really be in a 4 ft tank. Now, you could have a 4 ft tank with that holds 65 gallons and it would change other dimensions obviously. I have no idea where you're seeing 75 gallons- the fish gets to 10 inches (25.4 cm). I did a quick google search and saw that one site said at least 75 gallons while the next smallest number I saw was 100 gallons. As I have stated before, we aren't aiming for the minimum. Especially when the "minimum" might be a 10 inch fish in a 75 gallon. Especially with "might give it away"- might isn't really going to work. You're going to have to explain the needs of that fish to your parents and either they can get a larger tank, or show them other fish that could work. It's like people getting into the hobby because of Finding Nemo, and then purchasing a hippo tang and throwing it into a 10 gallon tank because "it's cute" and not taking into account the needs of the fish. You really need to make sure that you're looking for the correct answer, rather than the answer you want. I saw someone with a bicolor angelfish in a 13.5 gallon tank once- did the fish "fit"? Well, technically because it was "small" at the time.... but I think we can all agree that it's not right.
Look into any of the dwarf angels. Flame angelfish have the bright colors as well as stripes, the misbar angelfish is also stripy with some yellow. The purple asked angelfish is also neat looking. You could look into some larger wrasses- the pink face wrasse is neat. You can do a tomini tang, bristlenose or kole tang. A marine betta could be a really neat centerpiece fish. If you don't mind feeding frequently, schools of anthias or chromis could be neat. You could also do a school of cardinals- there are tons of options that aren't huge fish.
