For showing the html I just use multiple browsers. My page must look good in multiple browsers, not in my editor. For the whole environment I just consoles with full logging, and running different parts. For database I have another specialized editor - much better than any IDE.
I have opened a couple javascript files in Atom. About 30, all quite short, about 50-100kB each. The total memory used by Atom was over 900MB.
Should I be just a brainless monkey, and be happy that it's fine? Well, my machine has lots of ram, but I need it to some other things as well.
For me Atom is just useless, I don't even get half of the functionality I get from Idea and it uses twice as memory just for beginning.
I think most of the comments to mine would be: just use the editor normally, no one is opening 20 files at the same time, just learn how to code, and have one small file opened.
So instead of learning some good tools, you just prefer sticking hardly to one regardless the pain. OK, good luck with that. I just need a fast editor with lots of functionality and great speed. Atom doesn't give me that.