Selecting suggestions from the address bar is possible using Emacs-style shortcuts (i.e. ctrl-n and ctrl-p), but not with the more accessible J and K keys commonly associated with Vim bindings.
I'd love to be able to move up and down the list of suggestions with ctrl-j and ctrl-k.
Not many browsers support Vim-style keys to select UI elements. This is a very dev-focussed feature, but then so are the Emacs-style beginning and end-of-line bindings we're used to elsewhere on macOS.
You are definitely a hardcore keyboard user 
Let me discuss our approach to keyboard shortcuts with the team.
You can come talk to me about it on Discord too.
Not sure this would make much sense: on Emacs the Ctrl-P (previous line) and Ctrl-N (next line) keybindings are the native way to navigate lines vertically. On Vim, you change to Normal mode and then simply press j and k to navigate. The suggestion here (Ctrl-J & Ctrl-K) is not "vim-style bindings", but rather a strange amalgam that would be difficult for users to discover.
I leave you to debate that
