Last year I changed our bedroom TV, and agree there is a lack of quality "small" i.e. under 49" TVs. (I didn't want an insanely large TV dominating the bedroom, but since we watch at lot in there, I wanted a decent picture).
I agree 4K isn't noticeable on a 40/43" set at 8 feet, but you'll be hard pushed to get a decent set at that size that isn't. More noticeable is HDR - which gives much better colours and brightness at any distance. (Btw despite what people say, there's loads of 4k, and quite a bit of HDR on Netflix and Amazon).
Problem is is that most sets of that size don't do proper HDR - the blacks in particular looks very washed out and unconvincing.
The "smallest" TV that does proper HDR and 4k is the Samsung 43KS7500 - which typically, is about £750. Any others are "HDR compatible" - which means they attempt to show HDR material, but don't have the hardware to fully support e.g. Dolby Vision or HDR10. We initially had an LG set that was HDR compatible, but not "proper" HDR - stuff like Grand Tour actually looked worse than SDR. Contrast was very poor, even in all resolutions.
If you're not fussed about HDR, Panasonic mentioned above is meant to be good (with the above caveat), or the Sony 43xd80. These apparently are the next best.
In 32", there's even less choice.