30amp power cord to 20amp breaker?
I don’t know if you ever got a proper answer.
Yes putting 2 20 amp breakers on a 30 amp service is fine. You will trip the 30 amp main if you draw more than 30 for any length of time.
We over subscribe breaker panels all the time you should plan on your peak load being 80% by code but you can have more total breakers than the service rating.