Here dis’s thoughts who focused on the ukulele for a few years
Honestly I’d just go to any decent sized guitar store and talk to the employees. I wouldn’t go super cheap but that’s less of a problem with the bari ukes because there’s fewer cheapo cxxp for those
The baritone would probably be really cool - they’re awesome. However they don’t really sound as much like the classic ukulele sound. It’s a touch closer to the guitar. So if he’s really into the classic ukulele sound, consider a tenor. Some real big guys play some real small ukes so it shouldn’t be a problem. I do love bari ukes tho they’re super underrated