Need help: PC randomly stutters and lags with light usage

Upgraded my PC within the past few months, possibly hardware defect?

Preface: zero issues while gaming.

When I'm scrolling either on Brave or Chrome or Edge -- my entire system will suddenly slow down and become jittery, almost like the refresh rate drops to 40 hz or lower.

I can have a YT video on full screen, and randomly have hitches. It'll go away itself, or if I un-fullscreen/switch tabs it fixes it. Other times, when scrolling on Reddit, it'll slow down and be very choppy and if I click on any other application like Task Manager to review the loads it goes back to normal. Other times, my File Explorer will scroll very jittery and then smooth out.

I’ve already tried quite a few things:

• Reinstalled Windows 11 multiple times (deleting partitions and starting from scratch)
• Disabled and re-enabled hardware acceleration
• Disabled MPO
• Updated all drivers (GPU, chipset, BIOS) (used DDU while in safe mode)
• Tried different refresh rates
• Swapped display cables and ports
• Tested with and without my second monitor connected
• Ran a few diagnostic tests like Prime95, FurMark and there were no issues.

PC parts / relevant info:

• OS: Windows 11 25H2
• GPU: RX 9070 XT
• CPU: Ryzen 7 7700X
• RAM: 32 GB DDR5