The answer used to be Yes. 32GB RAM was a spec I'd commonly try to get. As the other commenter has indicated, contemporary browsers have decent logic for unloading open tabs from RAM. Likely it's one of the many improvements made after Google Chrome received strong criticism for it's RAM consumption.

No, because they're not loaded.

Firefox doesn't load tabs after a restart until you click on them, and I use a tab unloader so tabs also get unloaded after a few hours (mentioned in my original comment that started this chain).

It's currently only using about 3% CPU.