Regarding the level cap, this could also be for narrative purposes. Since Level 20 is the highest level possible in D&D 5E (there are no epic levels like in 3.5), Level 20 characters are expected to fight against god-like entities (like in Throne of Bhaal) or even against actual gods. Based on what we've seen in Early Access, I agree with Elessaria666 and wouldn't expect much higher than Level 12 (if at all).
