I have a 3rd Gen, and have several dozen tabs open right now, with no issues, stutter or otherwise. One is playing a video, quite a few are also larger page/webapps (e.g. Gmail, Trello, Github in a large PR). I am have the 1440p version, and am plugged into an external monitor that is at 1440p, which should be further taxing the integrated graphics, but it's not showing. I can't imagine you're coming close to hitting any memory limits with just five or six tabs, so presumably something compute related?

What five to six tabs cause stuttering?