OK interesting notes on FF Quantum. RAM does rise and but didn't get a chance to break this system before I rebooted over other issues (installed WSUS Offline updates app). Need to continue using FF to see, but there was an interesting event last night I noticed. Left browser open all night accidently with PC on (1AM-7AM). The page had a video ad that was running over and over and when I noticed this AM FF memory had shot through to 7 GB on 8 GB system with one process at 6 GB! System memory was at 99%. I thought, "OK there goes Mozilla's claim to lower memory usage." It was an NFL football site on draft prospects. Well, I got FF closed and allowed it to finish over about 10 minutes, and when it finished system memory was all the way down to 20%. This was on a short boot of about 24 hrs.
This is unusual for a browser, and I never noticed it for FF. Usually system RAM will drop to around 40% or even up to 50% if the app was using 80% or higher when open. Also got a pop up from FF to send an error report to Moz which I did. I think Moz should cap RAM usage honestly at maybe 50% of system RAM or 5 GB or something depending on available RAM.
Quantum is fast and seems reliable. Gonna stick with FF and continue to study its responses. Its far (like light years) better than anything previous from Moz as long as the extension issues aren't a problem. Looks like it could be a good starting point for some kind of impressive improvements performance-wise...
BTW, dusted off an old XP PC and Chrome wasnt doing well. Tried FF legacy (52.0.5) for XP, but it wasn't working either. Laggy with the old app container freezes way too much. Streaming video wouldn't play. Downloaded SlimJet, and its working well on this old core 2 system here. So far only using 250 MB RAM but only one tab. Gonna start experimenting with more tabs soon.