Show the kitchen. Show the PLAN for the kitchen. If you want the least expensive option, it is tile, and the way to select is to bring home samples and look at them in your kitchen when to tops are on the cabinets.

I would not do quartz. Beyond that? We aren't seeing what you have, or what you plan or where it goes or how much.....

The first question you ask yourself is how LONG will I have the kitchen and what do I want.......long term. Divide the cost of what you really want, over that number of years.

The least expensive option is to add a 4" or smaller Taj segment and paint the rest of the walls. I wouldn't pick quartz or Dekton slab. You'd need to show a lot more info to get an opinion on the value and impact of Taj slab. Pics of your slabs and how it could look with the grain match, any windows, openness to other areas and lighting plan. Polished or not, cabinet design, material if wood and finish. For tile you can look at stone not used as counter. Dolomite White Link.

Tile could coordinate using neutral porcelain like Arizona Tile Invictus textured. Not on their site yet. At 11:18 in this 2024 IBS show video. New Tile & Stone Products Revealed At IBS 2024 - Arizona Tile (youtube.com) And 11:12 in this KBIS show video. Bulletproof Countertops, Ventless All-in-One Washer, Cantilever Stairs & More: Design Week KBIS 2024 - YouTube Tile shops will have other choices.

NO quartz as fake stone next to real will look bad, kind of like you cheaped out. Ceramic tile but look to choose the exact tile after the tops are in and most of the kitchen is done.

I agree with willworkman tile and wait until all the rest is in I aslo think wall color after all is in.

Use the same quartzite OR find a tile or mosaic that complements all the elements in the kitchen.

If you are running out of money, just leave it with painted drywall for now and come back to it in 2 years. A painted backsplash is perfectly functional while you wait. Just make sure your counter installer gets a nice tight fit with the back wall, so let him know there will be no backsplash for now and the back edge needs to look neat/clean up against the wall.

Pick your Taj Mahal slabs carefully. One lot of slabs at one of our major local stone yards has streaks of lemon green in it. It was very obvious when a couple was trying to ordinate with their white cabinets.