I agree with caution about built-in appliances. It hugely limits what you can have. My washing machine was built-in, sort of, but that only amounted to having a wooden door bolted directly to it, to cosmetically cover the part below the controls, so it was easy to throw out the machine and the door and replace it with a non-built-in one.
My fridge-freezer is built-in, it is too small, there is wasted space in the cabinet above it that contains some electrical points and usesless shelves, so they could have put in a bigger one. If I ever need to replace it, there is only one on the market of the same size. I have already replaced it once, 18 years ago, and even then there was only one option, and that one had the freezer on the bottom rather than the top as the original did, so the separate fridge and freezer doors could no longer be attached independently to the correct parts of the fridge-freezer. We had to bolt the two together, attach them to the fridge, and leave the freezer door to be opened separately after the fridge was already open.
Built-in ovens and microwaves are OK. Though if you have lots of counter space it might be better to have a free-standing microwave. You will have more choice, and it will be at the right height. Mine is above head height, above the double-oven. It's 20 years old and can't easily be replaced, because I think the ventilation slots built in above and below it also ventilate the ovens below. (The cupboards go all the way to the ceiling, so there is no back ventilation at the top of them like the oven installation guides call for.)