Browser scrolling intermittent lagging /high CPU use  

Hi folks,

Following annoying problem: On my Lenovo Thinkpad T420, 12GB Ram, Intel Core I5 2520m CPU, Intel HD3000 IGPU running Windows 10 20H2, sometimes scrolling in the browser (Brave Browser) becomes laggy and very CPU intensive. Like 100% instead of 5-10% even on old mostly textbased websites and you can literally see the screen buildup square by square. I switched to Windows 10 a good year ago and this problem has been with me at least since. Too be honest I still could not single out the definitve the trigger. It most often happens when I try to use youtube. Youtube then becomes totally unuasable. But sometimes it starts when I browse less demanding websites too. After a couple of minutes it now often subsides and goes back to normal again. Other non chromium based browsers (Firefox, Old InternetExplorer) dont help at all. Neither does closing all other applications.
Some background:
First I thought it is the the GPU driver, as there is no official support for Windows 10. I played with hardware acceleration in my Browser, found out switching it off reduced cpu load. I did a driver downgrade from the 4459 driver to the 4429 version due fiddeling with an external display. Reactivated Hardware acceleration, now it reduces CPU load most of the time again?
Last week I found in this forum that member nightmayor has created a custom driver version Custom Driver : Intel HD Graphics 2000 3000 Extreme Plus -by nIGHmAYOR and tried it out. Unfortunately, this lagging problem persists. He suggested it might not be a graphics driver issue after all so maybe I should create my own thread....

Any ideas?

Thanks very much in advance..

Victek said:

Have you tried turning off extensions to see if it makes a difference?

Not in Brave itself, but my Microsoft Edge Browser or Firefox is without extensions. It has the same problem..

Victek said:

Have you tried clearing temp files?

Yes, I regularily use Windows disk cleanup as well as go through the application data manually. Did you have some specific files in mind?

Victek said:

I went to Windows 10 "Settings" and typed in Storage. It shows how disk space is being used and includes temp files. There isn't a category for browser cache specifically, but hopefully that's included. I was thinking that maybe the browser cache has gotten too big on you PC...?

No luck sadly, currently the file size was just around 77MB.
My SSD has gotten old and is just 128GB so I am forced to keep the junk at bay

Victek said:

You could try monitoring the performance section in the task manager while using the browser to see if disk utilization goes high (along with the CPU) when you experience poor performance.

Disk utilization stays the same