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.

It always makes my heart sink when a client asks for a "no-maintenance" garden. It tells me they really don't care. In truth, any planting needs a certain amount of care. Plants, like animals, need care. It's true that they're slower than animals to respond to deprivation, but respond they do. And it's not a good look. You might not have a lot of time, or you may not be physically up to a lot of gardening. That's fine - you can choose plants that require a minimum of care and grooming, and if need be hire somebody to do that minimum. But it does require planning. A gardener actively engaged with their garden can (and will!) experiment, try new things, move plants around, notice when things are going right and wrong, and for them a garden is never finished. Contrast that with somebody who wants a garden they don't want to work in or at. They want a garden that is more or less "finished" the day it is installed, rolled out like a stretch of lawn and meant to "behave", to stay static. I can't do a garden like that! Plants grow! They change, the environment around them can change, and what might have succeeded one year is not going to do it the next. It is entirely usual for a planting that just nicely fits a situation to need complete re-planting a few years on because the individual plants have outgrown the site. That's work! It is entirely usual for plants to flower, and for those flowers to set seed and die off. It is entirely usual for some plants to shed leaves as part of their yearly cycle. This "mess" is treated by non-gardeners as a crisis, as a nasty surprise, as something the plants "shouldn't" do. Because it makes work. Well, sorry, but no garden consultant can change the laws of nature. If you want a garden, you've bought work, and if you don't want to do it, you're going to need to pay somebody else. That's fine. Just don't ask for what you can't have.

Or this.. love screens as dividers in open plan living, makes the space more interesting

No problem having diff flooring.