Hi Pauline Can you tell me where you are located (NZ/Aus, state?), and I'll give you info based on that, and point you in the right direction. Having said that, most tile companies have bars that can transition between tiles (or tile supply companies). If I were you, I'd look into these first, before choosing tiles, as you may find the transition bars ugly, or unsuitable. Some people call them T bars. They come in many variations, colours etc, but this gives a cross section example. The T part goes between the tiles. The other thing to do would be to ask a tiler near you.

Could you use the same glass as behind your cooktop for behind the sink? Kitchens generally use the same material for all the splashbacks or it can look disjointed. Have a look at photos of kitchens on this site to get some ideas.

Have you already sourced your tiles? I would expect most tile stores could help you find the edging tiles which I think are typically termed 'pencil' tiles for the style you have shown. We used bevelled subway tiles in our DIY ensuite. In hindsight we would have aimed to finish the brick pattern with 1/3 and 2/3 sized tiles (like in your pic 1) rather than full and 1/2 (pic2 and 3) to give a more even edge thickness/profile... Might not suit and we didn't use capping tile (I lost that arguement!) so it is probably more obvious in our bathroom, but just something you might like to consider.

I work in tiles and the normal splashback height is 600 mm. This is because overhead cupboards are usually this height above the bench top. In your case you don't have this so can do anything you like. If you tile to low 200mm etc the wall gets damaged - paint doesn't wear like tiles. There are many materials you can use as a splash back but most aren't durable eg Perspex. Glass and tiles have the edge. Textured splashes are in hence the hand made tiles. If grout annoys you use large tiles you can get them up to 1200mm long these days with rectified edges you only have 1.5mm gap. Use sealer on the grout, they are now easy clean. If you have the money tile to the bulkhead a much more luxurious look. Maybe in a charcoal. I don't know how these gaps are getting so dirty. I use spray and wipe with a toothbrush occasionally and it takes little time and always clean.