Ive read about scaling/colors being off with non-mac monitors etc
TLDNR: 4k, 27" in scaled mode isn't as good as 5k but, given the high price of 5k displays, it is a sensible compromise and is night-and-day better than any 1080p or 1440p display. Plus, scaled mode isn't compulsory and you can switch modes in seconds if you have a job that demands pixel-for-pixel accuracy.
If you are being paid to do colour accurate graphics or video work then you might have to worry about colour gamuts and calibration - in which case the Studio Display and Pro XDR come pre calibrated for various standards (which is nice). Otherwise, you can calibrate a display yourself (and even invest in a calibration tool) if necessary. In a flabbergasting development, more expensive displays tend to have better colour and wide-gamut support.
...but that is not going to be an issue for the sort of "regular stuff" you talk about, which will look just fine. In fact, unless you are going to faff around with colour profiles and stuff, a "wide gamut" display can just make everything look over-saturated like it was shot on "Kodachrome Gold".
Scaling... again, not an issue for general use. That pesky red-and-green "no good for retina" chart keeps popping up and while the source article does give a good description of the downsides of "scaled mode" (but with hugely enlarged/exaggerated illustrations in order to explain the effects), the good/bad chart on its own is hugely misleading about the usability of 4k displays. For one thing, it
only considers the scaled 'looks like 1440p' mode and ignores the fact that 2:1 'looks like 1080p' is perfectly usable on 27" or smaller 4k displays and 1:1 3840x2160 would be more suitable for the larger displays in the table. Also, remember, that 4k@27"
is effectively "retina" when viewed at arms length.
I started a longer thread about scaling at:
https://forums.macrumors.com/threads/psa-4k-display-resolutions.2345906/