There are a number of cats that fit the bill. I would suggest any of the smaller pims like pictus or albofasciatus if you want a group. These are slimmer, more active catfish and you can do better with a group in a 75 vs more stout cats.
Syno cats are more active than doradids but not as active as pims ime. You could keep syno angelicus or decorus in a 75. Theyre gorgeous and grow to a respectable size.
Doradids like raphael cats are usually not active during daylight hours at all.
If it were me personally and i was making up a 75 gallon, I'd go with one or two harlequin lancer cats(bagroides melapterus). Really spectacular looking fish, somewhat predatory and active, grows to impressive size but not too big for a 75 imo.
The white whisker cat (bagrichthys majusculus) is a similar fish, but in an all black appearance.