It’s fine as you show it, stopping at the window. No need to tile above it.

My best advice is to wait until your countertops are in before choosing a backsplash. You may find that once the Taj is in you want a different type of material for the backsplash. That much stone in one space can look a little heavy.

Agree with counters first then see. A simple backsplash would be nice due to the pattern in the counters. Let one or the other pull the focus.

Are you talking about the window above the sink or the one on the right? If you're asking about the sink window, then I think it looks good going up to the ceiling as shown in your last image. Of your two backsplash options, I like the first one. But I agree with the other commenter that you may want to look at a porcelain tile. Or do you have enough Taj Mahal to use that as a backsplash up to the cabinets/hood?

No rush. I waited 5 months after we moved in to bring samples home, pick one and to get the backsplash installed.

Also look at local independent tile stores for more choices. Some people on the forums have had issues with marble from the big box stores, so buyer beware. Also don't make a choice with plastic over the tile!

"Should I run it up to the ceiling on the window side too?"

IMO that draws attention to the differences in size and shapes of the windows. I'd stop the tile at the bottoms of the cabinets.

--not an expert

Of the two choices, I like the first one better.
However, I think you can find something better. It feels a bit too matchy matchy with the countertop

I like that counter to be the star and if at all possible why not use it for the backsplash too.

I agree with wdc.

Please wait until your kitchen is finished, especially your lighting. Backsplash options are infinite, and you can’t assess how they will look until you have the kitchen mostly done.

I agree a simpler tile will probably look best with your Taj stone. Most kitchens can withstand ONE star in the room, and that’s your drop dead countertop. Anything busy on the backsplash takes away from the elegance of your countertop choice.

Be patient and wait to decide after it’s all installed.