Horrible FPS Lock and low GPU Usage

Hello!

After playing Overwatch for over 150 hours I have ran into a really big problem that makes my game unplayable.

My normal FPS was high up (110-155 because of the ‘Display’ limiter) using Nitz’s “Best Overwatch Settings 2017” even on my old PC (around 70-100fps).

Yesterday (2020-07-27T22:00:00Z) I decided to watch some YT videos on how to make the fps higher and more stable to have a constant 144+fps in teamfights.

After about two videos on YT my game started getting laggier than getting smoother, I tried reverting back the changes but nothing worked like before

When I checked Task Manager my CPU got used at about 75% while my GPU got to only 35% (50% if I used EPIC Settings) while having only 50-70fps, even as low as 40 while in a moderately intensive teamfight

I have checked, with OCCT, if the GPU or CPU is overheating/having bad memory chips/overall being really worn, but nothing of that sort showed up.

From YT videos and blizzard guides I have done the following things:
- Changed Overwatch’s video settings
- Disabled HPET
- Used programs like QuickCPU, TimerResolution, Park Control
- Disabled background apps like Spotify, f.lux, Discord (even the overlay), Logitech G HUB, Malwarebytes
- Updated my drivers, installed optional beta ones, used DDU and reinstalled the drivers COMPLETELY
- Disabled and enabled: Game Mode, GameDVR (Both through the windows settings and through RegEdit)
- Restored default Overwatch settings
- Reinstalled Overwatch completely

I have read through almost 50 Blizzard Support Tickets hoping that one of those will help me but none did

From that day I have unbearable lag spikes and just a weird fps lock (55-70) that makes the game not playable for me.

I really wish someone here will help me because I really like playing Overwatch but currently its impossible.

Here are my PC Specs:
CPU: Intel i5-4460
GPU: AMD Radeon R9 390 NITRO
RAM: 16GB DDR3 3200MHz
OS: Windows 10
MOTHERBOARD: ASRock H97M-ITX