I recommend to start with kickstart if you prefer to customize https://github.com/nvim-lua/kickstart.nvim or Lunarvim for a full IDE experience to see what’s possible and go from there https://www.lunarvim.org/de/
Most works out of the box then. Start there and customize further to your needs
Good choice, however the number of supported languages is limited to things with language server or treesitter support. Meaning languages without this, like asciidoc, is not supported and might never be