SrtaA
Chrome uses a lot of RAM indeed, but all for good reasons, it's to make your site loads faster :D
And RAM high usage is not necessarily bad because it means your computer is doing its job. If it isn't being used, then you're not really benefitting from your computer's short-term memory. If it's too high, you can always find out which tab or extension is taking up the most RAM, and close it.
Oh, you said you have 300+ tabs open. Dear God, why soooo many? If you have a lot of tabs open, I suggest you to look at extension like The Great Suspender. It suspends tabs after they're inactive for a certain period of time. You'll still have it open in your taskbar, and you can always go back to them with one click, although it'll take a bit longer to load since it will have to load from scratch.
Your Firefox is probably slow because of the same problem too. If you have so many tabs open, it uses too much CPU or RAM. Not sure if there's a similar extension for Firefox as the one I mentioned above, but if there is, you can always try it and see if it improves the performance.
Of course, you can always use Edge, don't feel pressured by me. 😅
In the end, it's really about your personal preference. Don't mind us, web developers, even though it's annoying to debug IE, it's still our job and we're being paid a generous amount of money for doing our job. And I gotta say, although I still loathe IE, but Edge is at least much better than all of its predecessors.