Agree, in this case the upper is the line.

Sounds right. Use pencil tile to cap off the tile.

How about this side?

Side splashes are a personal preference. They drive me nuts and I never use them unless a client makes us. I put tile on the back only and use a bead of caulk to close the small gap between the countertop and side wall.

End with cabinet and do not do a side splash.

Ending the tile in line with the upper cabinet will look cleaner in the area most visible. For a more modern, symmetrical look, I would not recommend a side splash. Do use high-quality, washable paint to avoid potential wall damage.

Almost finished! Now trying to pick the grout line color. Looking at bright white, snow white or antique white. Any suggestions?

The unending DEBATE!!! I beg to disagree. The decorative back splash is a grown up, sophisticated version of the lowly and deservedly maligned, boring four inch solid surface riser. Where would THAT? end. Answer is the counter edge. If your fabricator cheated you of an inch there, you'd be screaming, as it is the most noticeable spot. Sorry to other pro's but, a cabinet ending which leaves this inch ( less or more) of counter/wall exposed, looks like you ran short and indeed...........very odd. As the photo just above, and again, sorry........: )

I am to the point of suggesting if you can not bear this ending, plan your upper cabinets with an inch added ( beyond the lowers).....knowing you will have that extra inch below as the counter top is plus an inch to protect lower cabinetry sides. JEEEEESH!!!!

( going beyond a counter edge is just as bad, and lets not go there either lol )

I would have ended the back splash with the end of the counter in this instance. Having said that I think I would choose a grout similar to the counter color if you want to define the brick pattern, otherwise choose a grout that is the closest to the white subway tile.

I also would have taken the tile to the end of the wall where there is such a small space and no side backsplash, I do like white grout in kitchens i find they always get dirty