This is an interesting idea but Firefox itself should both limit resource consumption and do those sorts of stops. Hmm.

This feels like a Band-Aid instead of fixing the root problem. I've never seen this happen, maybe you have a bad plugin causing it? Turn off all your plugins or start a new profile, then turn things on one at a time.

partner uses Vivaldi which has a very practical option to disable background synchronization for all sites and make exceptions for some.

i can't see something similar in firefox/librewolf preferences

from my experience things like this generally don't work to well. The problem is that once its at 100% the sytem is bogged down so it won't actually kill it till the tab has calmed down and you can interact yourself again. Granted it might still get it before it spikes again so im not saying its without merit. Just warning to temper expectaions if you do find something like that.

Good idea. For me it’s Google Drive and gmail.