Here is my problem : After playing TESO, Fortnite and probably others game I guess, my desktop is super laggy, whether I am moving my cursor on the 144 Hz main screen or the 60 Hz one. Every thing is laggy, from the cursor as I previously mention to any youtube video. But after when I launch any another game that is full screen such as LoL or Fortnite (again), it's perfectly smooth. If it matter, Civilization VI, League of Legends, Chivalry doesn't create this problem. In addition, after maybe 10 minutes to one hour, my PC goes back to being smooth, for no reason what so ever.
But the weirdest thing is that when opening AMD Radeon settings, or enabling/disabling Radeon Relive, my PC is perfectly smooth for a second and go back to being laggy.
I'm running a RX 480 8 Gb, a classic i5 4670, 16 Gb of RAM and a 144 Hz FreeSync monitor, and that's probably the only component relevant I think.If you need any others informations to solve my problem, no problem.
Thank you for trying to help me and sorry for my english level