I have the same problem, On fortnite i have FPS drops. It was stable 85- 60. Now i play with 20-40 but more stable on 20-30.
Information and specs of the laptop:
Dell inspiron 5567
Graphic card: AMD R7 M445
Driver version: Adrenaline 18.5.2 (the fps drops also happened in 18.5.1)
Windows 10 64
CPU: I7 Intel 7500U @ 2.70Ghz (4cpus) ~2.9
Bios : 1.2.3 (as written in dxdiag im not sure if thats what you need)