Very thorough article! I’d be interested in an updated version.
3 years isn’t that long but in that time LSP has “happened”, so I would rather use an LSP server for actual code editing so I get a consistent experience with editing other languages. I should be able to edit lisp using the same LSP client (vim-lsp, ALE, neovim native LSP etc.) and therefore the same mappings I use in e.g python and typescript, to get completions, go to definition, find references, semantic highlighting (although this is presumably much simpler and easier to do with regex in lisp than lots of other languages).
The really interesting stuff (to me) in the article is about the REPL integrations and debugging, so having that decoupled from the editing support would be very interesting.
For Neovim, nvim-parinfer is a great plugin. It automatically inserts and removes paretheses based on indentation, which makes it much easier to change structure of code.