This happens in all programs and games. They include: Fortnite, Rainbow Six Siege, Minecraft, GTA V, Sony Vegas, etc.. This happens if drivers are installed or if they're uninstalled, although, the lagspikes tend to last longer with drivers installed. Even Discord freezes for a few seconds upon Alt + Tab-ing out.
PCPartPicker list: https://pcpartpicker.com/list/fLTqkd
Radeon Settings > System > Software > Copy All output:
Radeon Settings Version - 2018.0516.1451.24901
Driver Packaging Version - 18.10.16-180516a-328911C-RadeonSoftwareAdrenalin
Provider - Advanced Micro Devices, Inc.
2D Driver Version - 8.1.1.1634
Direct3D® Version - 9.14.10.01334
OpenGL® Version - 6.14.10.13521
OpenCL™ Version - 24.20.11016.4
AMD Mantle Version - 9.1.10.0254
AMD Mantle API Version - 102400
AMD Audio Driver Version - 10.0.1.6
Vulkan™ Driver Version - 2.0.20
Vulkan™ API Version - 1.1.70
Radeon Settings > System > Software > Overview output:
Radeon Software Version - 18.5.1
Radeon Software Edition - Adrenalin
Graphics Chipset - Radeon (TM) RX 480 Graphics
Memory Size - 8192 MB
Memory Type - GDDR5
Core Clock - 1303 MHz
Windows Version - Windows 10 (64 bit)
System Memory - 16 GB
CPU Type - AMD Ryzen 7 1700 Eight-Core Processor