I see, so it depends on each plugin. I came across quite a few plugins that use the modifier CTRL with F-something combination but so far all of them also triggered the plugin that's on F-something with no modifier so I didn't (and in a way still don't) see a point of using modifier with F-keys. I guess it's trial and error type of thing than.
I already burned quite a few hours rebinding in configs but regarding modifiers and F-keys the result is always the same.