I use https://addons.mozilla.org/en-US/firefox/addon/panorama-tab-... and have been really happy with it.

You can also try https://addons.mozilla.org/af/firefox/addon/conex/

Works similar to tab groups, but each group is in it's own container.

There's also Panorama view: https://addons.mozilla.org/en-GB/firefox/addon/panorama-view...

IMO yes, and I've tried a few. It's only really now that the new tab group plugins have reached parity with the FF56 versions, but they have done :)