Does your version of Firefox have the task manager feature - here, (using
FF 115.18.0esr on Windows) that's offered via the application hamburger
menu (at extreme rhs of toolbar in my FF) - More tools - Task Manager
... and it runs in one tab a monitor tool showing memory & cpu
consumption of each of the tabs that FF is processing. You might be able
to judge better which of your tabs are the hogs, if you can run that.
Thanks for drawing attention to this. It's very informative. One real pig is facebook. Even though I have one tab open that identifies itself as Facebook, the Task Manager shows two tasks, consuming 108 MB and 34 MB (but the sizes keep changing). I don't have any google tabs open, but Task Manager shows one occupying 79 MB. Another surprise was a tab that I keep open displaying the Real Time Operating Grid at the Energy Information Administration (EIA). It's usually occupying 90 MB but if I scroll the page it jumps to 216 MB.
I use KDE. One feature of the window manager is that I can "window shade" a window by double-clicking in the title bar, which reduces its screen space to its title bar — and double clicking unrolls it. A Firefox add-on that idles any tasks in "rolled up" windows would be useful.