Graham, pardon me for being cheeky but my Mum taught me that if you don't ask you don't get.
Would you be so kind as perhaps explaining with a tutorial on how you go about making custom profiles for both camera matches and to maximise image quality?
I think you would be better asking
@Dave Canon as I've only done it once, using LumaRiver and for Capture One. The latter adds to the complications because it uses a dual curve profile.
The exact process will vary with the program you are using for your raw processor, but you need to photograph a colour checker card with squares of known colours,
Then you then run those files through a bit of calibration software, that compares the known colours on the card with the colours rendered by the camera, and your raw processing software.
Using this data, the calibration software creates a profile that makes corrections to the image rendered by your raw processor so that the colours you see on the computer screen will match the original colours on the colour checker calibration card. Assuming your monitor is also colour calibrated.
You then make this the default profile for that camera with that raw processor.
In theory, this means that regardless of camera, the colours rendered on your computer screen will always look the same and accurately match the colours on the colour checker card.
With Lightroom/ACR the process is relatively simple, and when you buy a colour checker card from someone like Calibrite, you get the software for free, and it runs as a Lightroom plug-in. Actually, I now realise I lied earlier about only doing this once, because I've also made calibrated profiles for Lightroom
Making "good quality" custom colour profiles is actually rather tricky, but the mechanics of using the Calibrite colour checker with Lightroom is relatively painless.
The problem comes from us not actually liking accurate colours, but the process above is a good start, especially if you work in a museum making copies of paintings for archival purposes, or if you want different cameras to have the same starting point. But the commonly used Color Checker Passports don't have enough colours to make them suitable for "scientific" photography, ie the museum example above.
There are lots of Youtube videos that go through the process
e.g
View: https://www.youtube.com/watch?v=fLQTSQBd2jc&t=648s
But it's also worthwhile having a read of the Lumariver manual, which gives some background into creating profiles.
It's something that 99% of photographers can probably ignore, but as well as the convenience of having colours match across different cameras (at least more closely than they would without calibration) it also squeezes out the maximum quality from your sensor in terms of colour gradation and gamut.