Modern browsers have multiprocess architectures that ensure tabs are isolated at the operating-system level. So other tabs shouldn't affect the performance or stability of Construct 3. It even means crashes in other tabs are isolated and won't take down C3 as well.
If you open 100+ tabs, you're giving your computer a huge amount of work to do. It's like opening 100 different apps on your desktop. You have a finite amount of computing resources available, and it's amazing it can even handle as much as some people throw at it.
Yes fair enough, I try not to anymore.. it just happens. Currently I'm at 70, lately I've been at 30 to 40.
As far as resources though, I wouldn't pretend to be as knowledgeable as you on this but I'm not sure that's correct. I mean, with all those tabs open I don't see it using up the majority of (or even a significant amount of) my RAM or CPU %.
I have 70 tabs open in Firefox currently at 1.2 GB of RAM and 5% CPU utilized (i7 6 core 5820k). I've never seen it go above 3 GB of RAM usage for my browser (though granted, anything close to 2 GB is excessive).
[Though, I use a load-tab-on-click setting, on startup, so maybe only about 20 or 25 tabs are currently loaded.]
Anyway, so I'm well under my resource usage, but if it's going along fine, and I either open too many more (while still having plenty of RAM & CPU free), it can crash the whole browser/slow it all to a crawl, even if you close tabs --OR-- if it's ok like it is now, but I have 20 or 30 open, and I don't open more but leave it that way a few days, I see it crash or slow to a crawl plenty as well.
My understanding is that this is caused by something called "desktop heap" from Windows that seems to be a finite resource that doesn't properly get freed up again when you close browser tabs/windows always.
An issue since XP I keep hoping they'll fix..
[I could be wrong of course, and you're not my tech support for browsers issues, but that's what I was under the impression on as causing this issue.]