The great thing about hanging around here 'til they pull the plug plus going nowhere else is that the continued dwindling of my stream is a natural weaning-off of my social media cravings. No withdrawals.
Vivaldi makes it a little harder to see if you look at individual processes because of how it splits out different PIDs, where Firefox lands under one. But when I watch total memory consumption, there's little difference.
So it looks like heavy RAM use in the browser is just a reality I'm going to have to live with. I've been flipping back and forth between Vivaldi (Chromium-based) and Firefox, and there's really no daylight between them in my typical usage.