I have used the DxO product for about the past 20 years and I did not buy PhotoLab 5. The DxO product had two great features, so far as I was concerned. It was catalogue free and it had an outstanding lens profile correction, chromatic aberation correction and fantastic noise reduction algorithms. The downside was a rather awkward user interface and a somewhat slow response rate when loading up images. My second raw processor is Capture One and while I am no expert in using it, the camera tethering capabilities are something I use in the studio all the time.
I have used Photoshop for over 18 years and I have had to use that functionality twice in that period because I had to prepare some CMYK images for offset press printing. I'm not sure why you need to get into that functionality at all.
sRGB, Adobe RGB and DCI-P3 all use the D65 illuminant. THe very popular ProPhoto RGB used D50. Digital photography has traditionally used D65 but the offset printing industry has traditional used D50. Daylight colour films tended to be set for 5000K white balance and the daylight and electronic flash tend to be in the 5500K - 5600K range, so there is no magic about D65.
There is more to photography than skin tones; saturated reds, greens and blues (think flowers, fireworks and coloured lights). The sRGB colour space has problems with those hues. If you are posting your images on websites and use a low end,non-colour managed displays, sRGB can be as good as it gets. Do any high quality inkjet printing of saturated colours and you will want and need a wider colour space, I virtually never work in sRGB and I default to either Adobe RGB or ProPhoto RGB, depending on the image characteristics. I have a number of images that look terrible in sRGB, especially when using the Relative Colorimetric rendering intent.
Grahame's issue has nothing to do with the colour space he uses. There seems to be a problem with his computer as my Windows 11 computer does not display any of the issues that he has reported.