TL;DR Can’t use HDMI/DisplayPort directly or internal dGPU on Thinkpad (dead hardware). Thunderbolt GTX1050 eGPU available only. 1440p 144 Hz monitor only works on X11 at 120Hz or lower.
Specs: Thinkpad Extreme X1 first gen
CPU: Intel(R) Core™ i7-8750H (12) @ 4.10 GHz
dGPU: NVIDIA GeForce GTX 1050 Ti Mobile (dead, see below)
iGPU: Intel UHD Graphics 630 @ 1.10 GHz
Memory: 16 GB
I’m in an unusual situation where I had to disable the dGPU due to hardware failure as it was making the laptop crash regularly. I’ve fully confirmed that it is unsalvageable.
My understanding is that I can forget about ever using the HDMI and displayport directly as the dGPU controls that in some way. Neither works as far as I can tell.
For whatever reason, I have a Lenovo Graphics Dock, an obscure piece of hardware that features the exact same (I think?) GTX 1050 as a thunderbolt eGPU. The dock works and connects without hassle. It’s recognized with nvidia-smi. I am able to game with it, insofar as you can actually game with a measly 4GB VRAM. 
Worth noting that I am on 580 drivers because recently Nvidia dropped support for Pascal cards such as the 1050 (RIP) As far as I can tell, the specific drivers are not the problem because this occurred even before this support drop.
However, when I connect to an external monitor (supports nvidia g-sync and amd freesync; 2560 x 1440 IPS WLED; DisplayPort: 165 Hz, HDMI: 144 Hz) with Wayland, screen tearing is so bad that it’s unusable.
Some ideas that have not worked so far:
__GL_GSYNC_ALLOWED=0
__GL_VRR_ALLOWED=0
KWIN_DRM_USE_EGL_STREAMS=0
KWIN_DRM_USE_MODIFIERS=0
in etc/environment (did not notice changes)
LatencyPolicy=ForceSmoothness
Or
LatencyPolicy=Low
in ~/.config/kwinrc removed the tearing, but replaced it with lag massive enough to give me suicidal ideation.
The only thing that has worked so far was switching to X11, where there was little tearing but a lot of random green dots polluting the screen, which were themselves fixed by forcing 120Hz or lower.
On another Thinkpad (work laptop, X1 carbon 5th gen) with no dGPU but a working HDMI port, I can use Wayland by connecting the HDMI to the Thinkpad itself as opposed to the dock. I would have done this with my personal laptop but as mentioned previously the HDMI is done for, and I can’t install games on the work laptop by definition.
Should I give up Wayland altogether? I don’t want to start a religious war here; all I want is to be able to eke out the best graphical performance I can get away with with my nonsensical setup. There are some Wayland features I do like for example I can configure mice way more easily.
Thanks for reading so far and let me know if there is anything I can try, or any logs I can provide. I really am a noob in this specific domain so any ELI5 is appreciated. I posted on Arch forums already but nearly got banned once they found out I was on Cachy 