Python is probably faster than Elisp (or at least at the same order of performance), and Emacs is fine performance wise. And when Emacs is slow, generally the problem in those cases are architectural/algorithm decisions of Emacs, not because of Elisp itself. And like Elisp, if Python is really slow for some specific part of the code (for example, a function that is used everywhere in the code and it is expensive to run), you can write it in native code (i.e.: C) and call it from Python.
So I can totally see a text editor written in Python being fast enough, probably faster than an editor written in Electron since the runtime is much smaller (Node is faster than Python, however Electron runtime includes a whole browser with it).
So I can totally see a text editor written in Python being fast enough, probably faster than an editor written in Electron since the runtime is much smaller (Node is faster than Python, however Electron runtime includes a whole browser with it).