My Drizzle was semi-similar.
We got him as a baby, and he would eat and eat and eat. Usually, only about 2/3rds of a bowl, then finish that off. I had to fill his bowl twice a day, usually, when he was a baby. He never drank a lot then, but he does now - we'll let him drink from the sink (as if we can stop him, lol) and he'll sometimes go for 5 or 6 minutes. When he was a baby, his.. uhm, poo, as you mentioned, was also quite... like you mentioned. LOL. Odd thing to talk about, eh? Poo.
He may just be a growing boy, but you did say he was 2, right? He may just be hungry-hungry-hungry. Perhaps a bit under-fed? If he was in a vet, he may not have had as constant attention as he does now and might have been starving without them knowing. You never really know.
He sounds OK, just hungry, too me, but I'm a first time cat owner and both mine are from pet stores (well, one was free outside of a pet store) and where babies when we got them, so... I dunno.