> I gave up Sublime because of memory usage
Isn't this just because of GPU-mapped memory/textures? Because you can't get much better with any other app, for example text-rendering is not a solved problem yet, there are few nice tricks but they always come with some tradeoff so if you want to support non-english scripts, you usually just go with glyph atlas which needs to include 1:1 glyph-size (retina is big) + up to 3 extra variations because of kerning for each used glyph. System apps do not report this if they are using cocoa but a similar overhead is still there.
Or because of the emoji font, which alone takes 200M!!! And if your app opens it (just to support emojis, not necessarily to draw them), it gets reported as its own memory even when it's usually mmapped and shared between processes (and might not even be loaded in the memory).
What kind of memory usage are we talking about? And how did you measure?