First Question - yes, you can have the output from the transfer switch be a RV plug.
Second question - Your output from the inverter can be hard wired into the transfer switch. No plug needed.
You really know what you are getting into with an automatic transfer swich? Once you start figuring out everything you need for an automatic transfer switch and the money it will cost - not to mention the cost of the solar - you could buy a generator and a lifetime supply of gasoline three times over.
A manual transfer switch would cut the cost in half±.