The fzf.vim plugin allows you to do
speedy fuzzy searches for filenames and line-by-line content.
Once you've narrowed down the results and found what you're interested in,
you can hit <enter> and a new buffer will open over what was already in
the window. You can also open that file as a split.
Hitting Ctrl-x will open the file under the cursor as a horizontal split.
Hitting Ctrl-v will alternatively open that file as a vertical split.