Tub Flange and level tiling
If the tub flange is close to the wall, you can carve out the back of the wallboard so the flange is tucked into the cutout and the wall plane is the same.
I don't like the wall material above the flange, I think it's a stupid application. I shim the wall to the flange thickness and overlap the board on the flange, keeping it off the tub bottom by 1/2". This way, the gap is covered and water can't get behind the wall.
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
B. Franklin 1759