For me, though not blown the dust off it for emacs is to simply use direnv with nix and direnv will set your bins to the correct lsp server configured correctly for that project via nix and then load it using eglot (I have set eglot purposely to not load by default for as you say it can be slow and not always what one wants to load especially for small edits).

I have to agree with your comment about lsp in general they feel a little over engineered or old tags are nicer and feel less bloaty even if less powerful.