Limiting resources sounds cool. I wish I could at least determine why Firefox sometimes goes out of control eating everything. Setting a resource limit per page would be good too. Sometimes my whole computer is ground to a halt, but closing a single tab fixes it. Often not a page that is obviously doing much. Certain ecommerce sites are frequent culprits. Doing something in the background.

Firefox can tile two pages now: https://blog.mozilla.org/en/firefox/split-view/

I use Zen as my primary browser. Vivaldi is my chromium backup for when something isn't playing nice with Firefox, and for installing PWAs. Vivaldi is great. I used it for years before Zen came along.

+1 for Vivaldi. I keep expecting to hear that I've became out of the loop and it's turned into Brave without my knowing. It's a great concern. But so far, so excellent!