Welcome to reef2reef !!
I went from my 20 gallon with HOB filter to a innovative Marine Nuvo 20 and I don’t regret making the change. It looks so much nicer and hides all the equipment. You can keep any type of coral but some good starters are zoas and lps coral. Like hammer, frogspawns , torches, and Duncan’s. Some cool fish are blennies, they have great personalities and are fun to watch.