One thing that wasn't mentioned is the max sustained screen brightness for SDR, which is higher on the M4 Pro (1000 nits) compared to the M4 Air or M1 Pro (500 nits).
There’s an awesome app called Vivid which just opens the HDR max brightness. I use it all the time with my M3 Pro when working outside and I believe it also works on earlier models.
There are so many base features that are inexplicably relegated to 3rd party apps. Like a better finder experience. Or keeping screen on. Or NTFS writing.
Welcome to the Mac ecosystem. Where basic functionality is gated behind apps that Apple fans will tell you "are lifesavers and totally needed in Windows/Linux/etc)" for $4.99-14.99/piece. And, when they get popular enough, Apple will implement that basic functionality in its OS and silently extinguish those apps.
And that's when they let you modify/use your OS the way you want.
I don't mind that. 3rd party Mac utilities are nice: well designed, explained and do what they're supposed to because someone makes a living of it. I'm happy to pay these prices.
A far as I understand Windows only has a toggle for HDR on vs off, that's not what we're talking about here, this is about forcing the full brightness of HDR always, even outside videos. It's something that manufacturers don't allow for as it reduces display life, it would actually be an anti-feature for a consumer OS to expose as a setting. It'd be like exposing some sort of setting to allow your CPU to go well beyond normal heat limits.