Earlier quoted context omitted.
I upvoted you but... How comes Emacs is laggy for you? I'm running a beefy Emacs setup and it is really responsive. If anything Emacs in the nineties was "Eight Megabytes And Constantly Swapping" but... We're in 2021 now and now it's still 8 MB, so it's a rounding error (I'm only exaggerating a bit). It's one my lightest app: starting Emacs, eval'ing some elisp, and exiting takes... 81 ms. Eighty-one milliseconds. To…
I know that these "works for me" discussion are often not fruitful. But, I'll ask this: have you done a several hour session of typing/programming into a JetBrains IDE? I'm claiming that on my work Macbook Pro, even just typing plain text into a file and scrolling lines in IDEA is smoother and more responsive than doing the same in Emacs. I use the Vim plugin for IDEA and evil mode in Emacs. Even things like holding…
Emacs is at least an order of magnitude more responsive than IDEA (or any other JetBrains IDE). Start with a stock Emacs, no extra third party packages loaded, to get a sense of performance. There is a lot of great Emacs Lisp code out there, but the opposite is also true: Horrible code written by folks new to Emacs and Emacs Lisp, that can slow down Emacs a lot and contribute to a degraded experience. Which is why I recommend starting from scratch and incrementally adding third party code/configuration (ideally, understanding the code as you go along and avoiding packages with lots of dependencies).