Ah, OK. I wasn't aware of those APIs, only things like OpenGL and Vulkan, but those are perhaps specific to 3D graphics rendering?
And windows managers in the context of Wayland are the same as Wayland compositors? Which compositor would I be using through KDE Plasma 6?
Thanks for taking the time writing this up, it is very helpful for my understanding (and I imagine many others' as well)! For the things I don't completely understand for now, this also gives me a lot of additional pointers for what to learn more about to get a better grasp. So it goes straight into my notes for future reference.
Sounds like I should dare to activate my dGPU and reboot to check it out now then :) My biggest worry was that it would be so severely broken that I wouldn't be able to switch back, but I know that is just an irrational fear - no way Tuxedo would've switched to Wayland by default if it broke their own laptops. But I've been a little twitchy about larger updates since I deleted KDE accidentally from not properly reading/understanding the prompts during update.