I'm pretty new to 5e, but in reading over Tasha's it seems that pairing Sharpshooter with the two new Feats "Gunner" and "Piercer," you could make a pretty gnarly firearms user. Since Gunner gives proficiency, you wouldn't necessarily be tied to any particular class, either. Given the freedom and viability granted by these new Feats, what would you all say would be a good class for a firearms user?

Probably Fighter for more attacks and feats. Could take something like Echo Knight in order to stay out of melee.