Prime offload might be same thing? IDK

It's the same thing. Prime offload is a tool made specifically for these optimus laptops (NVIDIA) and other switchable graphics systems (laptops with AMD GPUs)

Unless you have a solid reason to use Wayland, I strongly recommend to use Xorg instead. It works better with switchable graphics, and I think that you will be able to offload your games with it without the need to restart SDDM. In your Arch system, follow the installation instructions for the optimus-manager. Since you're using SDDM instead of GDM, it should work without the need of any tweaks.

I'm not sure if you're aware, but if you wish you can load the entire desktop environment with the dedicated GPU. It's more practical since you don't have to setup your games to be launched through the prime offload command. The caveat is that it uses more power, a downside if you use the laptop unplugged.