Subway, to the bottom of hood and shelf only........and all the way around at that same height.

Thank you! Here is another photo because this wall does not have a shelf I am thinking to almost tile to where the screws are so that there’s not a weird transition line from under the shelf to the wall with no shelf

I would have to use schluter on that wall right to the shelf. So maybe to eliminate that I go up a bit more?

Just keep the SAME height, and use white schluter. Get rid of the screws : )

I adore your kitchen. I'd never want to clean those kit kat grout lines. I'm personally not a fan of tile backsplash at all. I'd run a 5" backsplash of your countertop material and keep the rest of the walls painted. I have done this in my last two kitchens and food, grease, splatter wipe easily off of the walls.