When I set it to 75 Hz. in the XFCE display settings and it asks me to make it permanent, it reverts to 60 Hz, on the next boot. When I set it with xradr via .config/autostart nothing changes. Suggestions will be appreciated.
Might be with the graphic card not fully supporting 75Hz.
When You set it to 75Hz. and it is working,
go to Session and Startup-Current Session and Save Session and try logging out
and login again and see if it will retain the new setting.
For another problem (shadowing) I just bypassed the onboard graphics and connected a graphics card. Now it boots wit a 77Hz. refresh rate and all is well. Thank you.