running thwn wiring
I want to run 2 20amp circuits from my panel to an outside BBQ island. I have 3/4" pvc run underground outside to the island. It comes off the house in a junction box. My question is, Should I run romex from the panel to the junction box and then run thwn wire to the island or should I run thwn wire the entire way? Also, should there only be 4 thwn wires in the conduit for the 2 20amp breakers? 1 green, 1 white, 1 black and 1 red? Or should I run 2 black 2 green and 2 white?
Thanks for any help!!!