When I was using macOS regularly, CotEditor was my go-to text editor before I learned Emacs. Compared to XCode, Netbeans, and Eclipse, it had a miniscule memory footprint (somewhere between 10 and 20 MB). It wasn't as fast as Sublime for some tasks, like regex search, but had built in syntax highlighting support for nearly every programming language still in use, and it was very easy to create your own themes, with an intuitive graphical interface for setting colors for different token types.

Comparing it to default text editor I think is not correct, try to compare it to another code editor like VSCode, Nova, etc... it's very fast and simply, I love it.

In terms of startup speed and editing feel, I think it's pretty much the same as TextEdit.app, and much better than any Electron-based editor.