I've seen many matches were Velotti played great and he's got more hype going on than most of the other young argentine players coming up but, yes, in a way i agree. He fights hard, has some touch and solid groundstrokes but i belive size will be a huge disadvantage for him as he progresses in his career. He's very short, serve is attackable and lacks power overall. I mean, Schwartzman is even shorter and smaller but generates way more pace in all of his shots, to name an example out of that group. Arguello has the most potential by far IMO.
I agree about Arguello. He's the one of the young Argentine group to watch. I also like Andreozzi and Pella, and DelBo may not belong with this group but he's still young. Arguello has the biggest game of the young Argentines.
Velotti has hype for beating fellow 15-18 year old kids but out steadying them and having good feel for his shots. This is the big leagues and as you said, his game isn't big enough. That backhand of his is awkward, especially the slice he hits. He lacks a kill shot. And I think his footwork is mediocre. We'll see how he improves with more experience.