Currently on this machine: using 900MB of RAM, including all language servers, with nine open projects - that is pretty phenomenal. VSCode could barely keep one open with the same memory.
The perception of 'fast' is very subjective. To me having a smooth, jitter-free UI, low input latency, and instant startup, all matter a lot.
It's amazing that a gig of ram is considered lightweight for having 8 project dirs open in an editor, which normally means 8 tree views and a few open file tabs per project :)
Even more amazing that 10GB for the same purpose is considered acceptable. ± 100MB for window, project files, LSP servers, ASTs etc is something very few editors can achieve - I'm pretty sure Zed beats both Emacs and Neovim in memory consumption.
My experience with Zed differed. On Linux I found it to be very memory hungry.