I am not sure if you need the xf86-video-amdgpu package.
I would think the mesa package would be enough.
I am fairly certain your issue is caused by conflicting drivers - perhaps removing the xf86-video-amdgpu package and a reboot could provide some insight.
Test if removing the package help
sudo pacman -Rns xf86-video-amdgpu
For decades I have shunned AMD - but lately I have been investing in AMD based hardware and I have not been disappointed.
I have a Lenovo X13 gen.4 (AMD 7840U / Radeon 780M) and a Lenovo P620 workstation with AMD 7900 XTX GPU both using Wayland and Plasma - it work without any notable issues.
Your system is a slightly newer - which is why I suggested the newer kernel and the latest available in the repo on unstable branch.
Setting and odd scaling factor may be contributing - especially on X11.