Is there an issue with Wayland for your setup? I run Gnome + Wayland on Fedora, with two monitors with different sizes and different refresh rates - eerything seems to run pretty fine, including gaming?
Not OP but the last time I tried Wayland was about a year ago (also on Fedora) and I had similar issues using multiple monitors with different refresh rates, ended up switching to x11 which resolved it (using an nvidia card with nonfree drivers if that matters). But it seems I'll have to give Wayland another try if they've addressed it since then, I hadn't been keeping up with it.