I have a laptop with graphic card R7 M260 and first of all, I recently updated to adrenalin 18.2.1, while I play League of Lengeds i get FPS drop each game on team fights even with low graphics, so I have activated Chill but same issue and only this happens in League of Legends. I play other games like Fortnite Battle Royale it run smoothly with medium settings never got FPS drop and Pro Evolution Soccer 2018 and others games they works fine.
I deleted adrenalin and played League of Legends on the dedicated card Intel, it worked fine without FPS drop, so I reinstalled adrenalin again and wanted to switch to power saving mode in switchable graphics to play League of Legends on Intel but when I close AMD Radeon it doesn't save and automatically changes back to high performance, not only but with all applications i try to switch them it does the same thing.
i have the same problem with my R8 M435DX. Everything starts ok but after some minutes the fps drop in team fights. I also have a 1-2 second freeze when pressing "tab" (to see the game stats).
I'm planning to go back to the last version before adrenalin and test again.
I will keep you updated.