OK, I'm giving Thorium 122.0.6261.158 a try on 32 bit XP.
I still managed to crash an Instagram tab with an 'out of memory' message, but it was a great deal more difficult to do it with Thorium than it is with Supermium!
What seems to happen with Thorium is that as I scroll, the memory use does spiral up, but it gets to a certain point and then drops back again. I can scroll for a long time, and it keeps doing that, but eventually it does crash out. This is unlikely to happen in normal use though I would have thought.
With Supermium, the memory just keeps going up, and it crashes relatively quickly.
In most other respects the browsers seem to be pretty similar, although on one website I use regularly Thorium does not seem to be loading the web fonts, so the displayed font on the page is wrong.
With Supermium, it's fine. Maybe a setting in Thorium? I will have to investigate.