Question Computer struggles running multiple applications; this never used to happen.

[adza botchway]

Just the other day, i got my internet upgraded to 100/25 and i didn't expect that to fix all my issues but it has made it easier on my pc for sure. I also switched my OS from my HDD to my SSD and that has also helped significantly but one recurring issue is that whenever i open a game like runescape, rainbow 6 siege, minecraft etc, and i alt + tab out of it to go on google for a second, it'll just be really laggy and slow but when i look at my cpu usage, it's only at like 40% which is perfectly normal. sometimes task manager will say it's at 100% but when i add up all the percentages, its nowhere near 100%. I'm really just at a loss here.

note: all my drivers are fully up to date.
I've uninstalled and reinstalled all my drivers multiple times, in fact when I moved my OS, i wiped about 90% of my computer to clean out tons of junk but it's still acting weird.


Specs:
Cpu: 15-6500
GPU: EVGA GTX 970 sc
Cooler: hyper 212 evo
Ram: 16gb g.skill ripjaws
Storage: 1TB WD HDD/ 250gb samsung nvme SSD.

 

[Satan-IR]

What are full specs of your system?

 

[adza botchway]

What are full specs of your system?

Cpu: 15-6500
GPU: EVGA GTX 970 sc
Cooler: hyper 212 evo
Ram: 16gb g.skill ripjaws
Storage: 1TB WD HDD/ 250gb samsung nvme SSD.

(sorry, meant to put this in the main post.)