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?
I'm on Fairphone 4 with CalyxOS, and I am happy with that. I would not expect them to release a Fairphone 6 anytime soon, so unless OP has all the time in the world, the Fairphone 5 should be good if they want to go this route.