I just want to confirm this, but stealth essentially means nothing in this pairing, right? Also on a side note the thief can carry as many treasures as they wish?
Yes this is my understanding of the rules too. There are more implications. Flap stat is a poor upgrade choice because it means you are merely upgrading your useless stat. Also the Thief and Cave cannot "attack" each other, so back stab and unnatural evasion are also useless upgrades in this context.