The less grout lines the better. I’m so glad the mosaic tiles trend for backsplashes is over… even epoxy grout gets dirty or yellows. The only good thing with epoxy is that it won’t come off easily if you scrub it too much, like regular grout.

I think it’s too busy with your countertop. I’d chose something simple that’s a larger format and not use contrasting grout.

sorry these are stock photos. I don't have a counter top chosen yet

If you choose a modern high performance grout, and do not have a high BTU range without a back guard, then you will have zero issues. Too much heat from a range without a back guard can damage grout, sealers, and a whole host of things. Including quartz.

I would also recommend to stay clear of small backsplash tiles. Choose larger tiles that give greater surface area and less grout lines.

How often will the secondary kitchen be used? Where is it located? What kind of lighting?

With a wide, wide confusing world of tiles you can use on a backsplash, why not get something easier to install AND keep clean?

Backsplash tiles are chosen after everything else is installed. Houzzers are GREAT at helping you pick something once your cabinets and countertop are finished.

How lucky to have a secondary kitchen! Will it match your everyday one? I’m curious about how the two relate.

The backsplash is the “jewelry” of the kitchen..it is okay to leave it til last for aesthetic reasons…but over the stove can also be …a different more easily cleanable material…. to make maintenance easier..and even add a pretty accent feature in your kitchen