Where the counter ends.

It’s awkward, though. So, hang some shelving to fit over the end of backsplash.

to the end of the counter

Not sure there is a good answer for this situation. Extending the tile all the way to the edge of the the edge of the counter top always looks funny to me. If there is tile above the granite it seems there should be tile below it too. In this case perhaps ending it in line with the edge of the display shelves of the cabinetry might be the best choice especially if you can use a bullnose tile. A bullnose (I think) would provide more of a demarcation and would look like it was intentionally done instead of just being an afterthought.

Upper cabinets.

https://www.houzz.com/discussions/should-we-keep-or-redo-backsplash-dsvw-vd~5534465

No, do not go to the edge of the counter. That will look weird.

Stop at the end of the cabinets.

Also, recommend that the grout is the same color as the tiles or the BS will end up looking too busy.

Use a pencil tile to cap off the edge of the tile at the end of the cabinets.

You can go too far with a backsplash.

its personal.... i'm team orange.

i always think tile sticking out as in the blue arrow looks silly.

I love the colour of your cabinets but I would remove the frilly board over the sink.

Do you think white is the right color for the back splash. Perhaps something with a warmer tone would blend better = kind of bone white.

Be mindful that there are several colors of white. Bring home several samples. A super bright white might be too glaring. Nothing yellow but a soft white would be best. Where are you getting your tile? Home Depot? Lowes?

Home Depot. They only had 1 white subway tile. I hope it’s. Not too white!!

No turning back now....

You can do either or take it to the top.

The purpose of a back splash is to protect the wall from cooking/mixing splatters and provide and easy to clean surface. So, if you'll be mixing stuff on the peninsula area that could splatter, take the back splash to the edge and/or to the top. If not, make it flush with the cabinets. If you won't be mixing on the peninsula, I'd take it to the cabinet edge. It really depends on how you use your kitchen and what your aesthetic preference is.

To the edge:

To the cabinets:

To the top:

I had the same struggle when we did our kitchen a few years ago. I actually just had to to look to see what we ended up doing. I love my kitchen and agonized over some of the details. Whatever you decide will be just fine! FWIW, this is what we did.

Look for grout as close to the tile color as possible. You don't want to highlight the grout which will just make it stand out too much with a busy counter.

Would be ideal if you could extend those shelves to the length of the countertop. Then carry the backsplash all the way to the end. You could also carry the cabinet paint color onto the wall underneath the countertop and finish with some wood trim. I agree with removing the curvy wood valance above the sink. That will give an updated look and more light from the window. Hope you post a picture of the finish kitchen.