You can fit it on two sheets if you attatch them together on the long side. I used one sheet of maker foam (30x40) and I was able to fit all the parts on it. However, if you are cutting it out of 20x30 sheets it'll use three.
It should work as a 3 channel RET if you add enough dihedral, but I would recommend making it a AET and if you need, you could use one servo on the ailerons. I did it on one of mine and it worked well, but you have to route your rubberbands underneath the pushrods if you mount the servo to the top of the wing.
For that motor I would build it slightly smaller, probably 85 or 90%. You can use any 6” prop. The ones that come with that motor are pretty good, but if you have to buy another I would get the APC 6x4.