I was wondering if there was a way to watch youtube without it lagging because when I try to watch a video it just crashes and I have to shut down the computer every time.
Watching Youtube videos using youtube.com in my Chromium browser works fine on both my pi-top version 1 and 2. It works both with the latest images of Raspbian (setting gpu memory to 128) and pi-topOS (using out-of-the-box gpu memory of 256). Both in window and full screen mode. Both updated with
sudo apt update
sudo apt upgrade
On pi-topOS it can be a little bit choppy at times because it can run short of cpu time and memory due to the dashboard running in background and the lower cpu memory available. But I have never seen it crashing.
If you are not using the latest software version, I recommend downloading a fresh image.