Not sure of the difference you make between "dedicated" and "independent" HA instances, but I would suggest to have an HA dedicated to your RV, so that you don't rely on Internet access, so option 2, I guess.
Depending on what kind of intercommunication you'd want between the 2 HA installations, if any, you could use MQTT.
At some point, I created a custom component to synchronize 2 HA instances (MQTT DiscoveryStream integration), but I don't use it anymore, so is basically on life support from actual users...