Is fzf buying you anything over just using :grep? (If speed is the issue, the magic words are `set grepprg='rg --vimgrep'`, after which it's actually usable.)
The two features I really like about fzf are
1.) the preview window (visible here https://github.com/junegunn/fzf)
2.) Fuzzy finding/multi-selection/gradual refinement of search terms