Is my computer up to it?

Firefox with a few tabs open:

CPU maxing out? 70% RAM usage?
OK let's close Firefox:

Well, that dropped off!
And open Chrome:

CPU maxed out! Ram a little lower.
And let it settle down with a few tabs open:

OK, so I need to get scientific and open Firefox and Chrome with the same tabs open, but it seems that I've found the reason why my installation of Debian Buster (Testing as of time of writing) runs slow.

Back in 2015 when I bought this laptop, many reviews complained of mouse pointer lag - in Windows. An update seemed to fix it, but today it's back to the same condition- laggy mouse,and slow to open programs.

Have web browser become heavier? Has Debian become more bloated?

To me it looks like the web browsers are the culprit.