I went vertical so tall. Helps to raise height. It will also match your 300 floor tiles I have silver grout with antique white tiles. It’s a personal choice you can’t go wrong either way.

Just a suggestion but have you thought about a deeper grout to showcase each tile a slightly deeper grey to the tile will showcase the patterns so they don’t get lost into one another.. Plus so much easier to clean! If you’re afraid to go too dark then go two shades darker than the tile.. Either way will work.. but as a professional having used similar tiles I always like to showcase with a deeper grout.. Just a thought!!

Where horizontal and vertical meet should not be grouted because it needs something flexible, something we learned the hard way, twice, in different houses. Make sure your tiler redoes the waterproofing properly too.

The size of floor tile: 300 x 300 mm and the size of wall tile: 300 x 600mm The floor tile and wall tile do not align at all. It looks unprofessional. Should the tiler redo the job? Thanks for your advice.