Comment 2 for bug 1890802

This is expected. Fractional scaling in Xorg sessions works by rendering at a higher resolution than your screen(s). So that increases the likelihood of stuttering compared to integer scaling.

That specific issue will never be fixed because it's a required trade-off to get fractional scaling working in Xorg. HOWEVER, general performance will increase a lot in future versions like Ubuntu 20.10 so that hopefully will be enough to offset and eliminate all the problems you see.

As for fractional scaling making things slower than not scaling, that is expected and can't be fixed. If you can then please use Wayland instead.