What are your drywall/cement board/framing flatness tolerances for tile supporting walls?
Just use drywall cardboard shims or sistered studs to bring the studs into plane. TCNA says 1/4&quot; deviation over 10'. If using large format tile, trying to level with thinset after will take way longer and be more frustrating than the time it would take to make sure the walls are straight and plumb
Edit: Since you like Sal youtube videos this is the one you want https://www.youtube.com/watch?v=PCUWkbG060s