If your upper cabinets are 18" above the countertop, it can be a good idea to select a tile that can be applied without cutting the tile.

6"

2"

3"

18"

Totally agree!

No, it does not matter; pick the one you like best.

Depends also on what size grout line.

This is the image on the web site. It is stacked 5x5. If you find this beautiful, go for it. But it’s not too late to look for inspiration images and other tile options.