Split sub-panel box with dual feeds?
If you run two feeds into one panel, the current will flow through the lower resistance path. You will end up tripping the 20 A overcurrent limiter.

If you want to supply 50 A to your tiny house using a 30 A feed (the RV connector) and a 20 A (you don't specify 120 or 240 V) feed, divide your loads into two, and install two separate subpanels.

You may find you can run the entire home off a 30 A feed. 7200 VA is a substantial amount of power.