That's right. I put Romex in conduit for a short run from the outlet up to the floor joists, when I put a receptacle in my basement for a freezer. For five feet or so, you can push it through. If it is a complete conduit system, use individual wires.If this is a complete conduit system, as in box to box and not just a sleeve, then there is no reason to use NM cable in conduit whether it is legal or not.
Sure. Anything bigger than 12-2 I would put in 3/4 conduit just because it would be a little tight. My dryer (10-3) has 3/4 inch EMT from the floor joists to the receptacle.Can you use 3/4 conduit? 1/2 is tight.