You mentioned thoma would drink a lot of beer, which begs the question - would he have a beer belly 👀
Permanently? No. Belly full of beer, bloating him out? Absolutely. Now I know Thoma doesn't drink a lot of alcohol, though I think he might on occasion. This also could be during parties when he has to keep up pleasantries for the Kamisato Clan or Yashiro Commission. If business needs to be done, then it needs to be done. I also think if he needed to gather some intelligence for Ayato he would. However, I do think Thoma would be the type that would regret it in the morning and gets hangovers and has less tolerance than his Mondstadt blood would usually allow (Venti for shame).
But because of his capacity and he'd probably still eat lots of food to go go with it, delaying how drunk he'd get. But if he needs to, he can pound it away. I don't think it's uncommon for Thoma to stumble home, with his bloated belly making his black t-shirt ride up and expose the stretched skin while he keeps having to stop to keep things from spinning and letting out sickly burps the whole trip, rubbing his stomach gently to try to stop the cramps and let things settle.
I think he's far too active and wants to make sure he looks good for Ayato and Ayaka to let himself get too far out of shape. That is unless they wanted him too.
