>>note taking or chat apps need several hundreds of megabytes of RAM to run.

I have a fairly big app and while I'm not sure how to measure that I ran "about:memory" in Firefox and added up everything I saw for the app and it came out to be about 30mb.

My Mac's Finder says the directory with all the code is 9.9 MB.

That app is plenty fast, even on my old late `09 Mac Mini Mac running 10.11.6 with just 4gb ram.