I use coc.nvim with rust-analyzer and I find it amazing. I used a more lightweight lsp client in the past, but I find the more full-featured coc.nvim to be the best balance - I get all the benefits of an IDE + the productivity of vim. coc is based on the VSCode intelli-sense engine and enables inline type-annotations by default, but I am not sure if "regular" vim (not neovim) supports it.