You do know that a cange in counter after tile install is usally a bad idea aince the tiles almost always have to be removed before counter install. My advice wait get the new counter and do a 4 " backsplash of the same material always looks good and no stress about backsplash. It appears you have minimal space for backsplash where it really belongs so IMO a no brainer

I would do a statement tile. you don't have a lot of space to cover, so something that really makes a statement. Even a black embossed tile would look great.

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Your kitchen is very nice as is, and the view is the star. I can’t quite tell whether you already have a 4” riser in the same material as your counter. If so, that IS your backsplash. I advise against changing your countertop. Once you start swapping out/replacing one thing, you lose the overall cohesion that you already have. Stop obsessing and enjoy your lovely home and. VIEW.

keep countertop. do a mosaic backsplash in grey/black/white

Where?? The only place one is NEEDED is behind the sink and the window trim is pretty much there. I might have beefed up the trim to bring it all the way down, but then the cupboard on the left would be even skinnier which is already oddly small.

Your view is GORGEOUS! I'm not sure I would even notice a backsplash with that view. So, will suggest that you install a simple, white tile that will frame the view.

I would wait until, or if, you change the countertop. The one thing I would change is getting rid of the pendant hanging down, maybe just a recessed light above? The view, wow!