There are a few fairly easy SPS out there.
Montipora, Birdsnest, and Acropora, have some good beginner level varieties.
As far as anything that will nip at your SPS to consider, I remember you asked about Valentini puffers recently. I would use some caution if you have gotten yourself a Valentini. They can nip at SPS and LPS but aren’t always known to do so.
As far as tank sizes go? There’s no real seize requirement for coral. As long as other parameters are met all coral should be fine in any aquarium you choose. However, my personal recommendation is 40 gallons or more with a sump.