The common ones here are : 23 gauge- almost invisible but usually limited to about 35 mm length unless you want to spend a lot more and get one that goes 50mm. 18 gauge is the most popular, small hole, commonly available to 50mm length. 16 gauge is for nailing heavy trim work like base boards onto drywall.
It doesn't take a very large compressor to run one but you do need a regulator on it to control output pressure. That's what determines how deep the nails get driven.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.