Playing Alvarez on the wing is not an improvement on Grealish or Mahrez.
We do not need to change the way we play to play him behind Haaland - that's where KDB plays most games. His issue is there are 2 spots for him in the team taken up by probably the 2 best players in the entire league. KDB needs to move to accommodate Álvarez, not shoehorning him in on the wing.
Álvarez's skillset doesn't suit the wing much at all.
He's quick but hardly rapid. His ball control and dribbling isn't brilliant. He doesn't maintain possession as well as any of our other wingers. He has fantastic pressing, fantastic finishing, intelligent movement, and one touch/touch-and-move play. These skills are all underutilised on the wing.