[iLemming]

a) Build it with native-compilation flag

b) Use https://github.com/blahgeek/emacs-lsp-booster

c) Tweak GC vars, see: https://emacs-lsp.github.io/lsp-mode/page/performance/

d) Use plists for deserialization (described in the previous link)

e) Learn how to use built-in profiler and don't hesitate to launch it, sometimes simply disabling some minor-mode in specific setting is all it takes

f) Current state of Tree-sitter in Emacs is a mixed bag - for some modes you get huge improvements, for others it's the opposite. YMMV.