PC Stuttering

Hey all,

So I have just setup a system for my kiddo using a combo of some old & new components, with a fresh Windows install. Unfortunately it is suffering from annoying stutters when moving the mouse when doing basic things like loading an average webpage or watching a YouTube video, even though CPU, RAM, GPU are underutilised. Surprisingly, I was able to play Apex Legends on high settings without major problems, other than the slight stutters from time to time when moving the character using the mouse. The game was butter smooth otherwise. So the system seems to be more bothered by loading a web page than running a game, whatever that means.

I have run WhySoSlow and LatencyMon. WhySoSlow identified an issue with BIOS & Chipset behaviour, stating highest measured SM BIOS interrupt or other stall being 174 microseconds. LatencyMon has similarly identified that the system can't handle real time audio. I have attached LatencyMon logs.

Can anyone help with any suggestions on what else I can try to resolve this?

Thanks for any help!

What I have already tried:
- Updated BIOS to latest version
- Tried using both standard drivers that Windows 10 installs, and also updating chipset, audio, etc drivers from ASRock website even though they are quite old
- Reinstalled Windows 10
- Physically removed the GPU and re-installed Windows 10 using only on-board VGA
- Changed wireless mouse
- Changed wireless mouse dongle between USB2 & USB3
- Changed wired keyboard
- Disabled CPU throttling in power settings
- I've tried running WIndows Performance Analyzer, but I don't really know what I am looking for. Did not see anything that sticks out
- Had a look in BIOS to ensure CPU was not being throttled. Checked other settings - nothing stuck out to me, but I'm not an expert.
- Checked mobo, CPU & GPU temps - all good.
- Wanted to test running in safe mode with networking, but unfortunately my keyboard (Anne Pro 2) will not work when Windows goes to the troubleshooting menu/screen.

My hardware:
Mobo: ASRock Z87M Extreme4
CPU: Intel Core i5 4670K. No overclocking.
RAM: 8GB of DDR3. No overclocking.
PSU: EVGA 650W
GPU: GeForce RTX 2060 (I did try physically removing this card and re-installing Windows again using on-board VGA, with no change) No overclocking.
Peripherals: Wireless mouse and wired keyboard

It could be as mundane as a flat battery in the Wireless mouse/keyboard. Also a possibility of power saving/green settings of those wireless components.

The obvious thing to do is plug in a standard wired mouse and standard wired keyboard. Just to try and isolate the problem.

Uninstall and Re-install Chrome Browser.
Chrome Settings > Advanced > System > Use hardware acceleration when available, try Off as well as ON.
Same thing applies to Edge.

Un-install the Nvidia graphics driver version 456.71 and use an older one.

LatencyMon always comes up with that bit about real-time audio, It does on mine though the sound is perfectly OK.