I have mixed refresh rate monitors, and animations and stuff will use the lowest common denominator. So all animations will be in 60hz on my 144hz monitor, just because I have a 60hz secondary monitor. The biggest offender is moving windows around.
I still haven't encountered any issues on Wayland on GNOME. X11 is unusable for me because it handles multiple monitors poorly, and everything just seems less smooth.
Can't you just plug your phone straight in and transfer the file? I still prefer KDE connect though.