When talking about a "Federation Fighter'" you're probably referring to something the size of, and with the capability of, a small Klingon BoP. The some general category. In Vanyel's video each of the fighters were doing as much damage (size of fireball) to a Cardassian ship, as one of the main phaser strips on a following Galaxy class firing a equal number of shots at a similar target.
So a totally stripped down starship, just a warp core, engines, weapons, shields and life support. Nothing else. It's phasers (as stated) the equal a segment of a Galaxy's strip, perhaps only good for several dozen full power shots.
It's photon torpedoes the same as the larger ship's, the fighter would lack the larger ship's launch accelerators, but for near point blank range firings wouldn't need them. The torpedoes might be carried in simply "drop" bays or mounted externally.
Because of the smaller space of the enclosure, the shield generator could project a full power field around the fighter. The generators (run at maximum capacity) wouldn't have to last for protracted periods, a few hours at most. Between battles they would be swapped out.
I wonder about the "wings." Shuttlecraft and runabout don't possess them and so why does the fighter? The Klingon BoP has them too and doesn't have nacelles, the fighter (and the BoP) might have a different form of warp coil, different shape, that is housed in the wing.
A science officer might want to use one to go check something out up close, without having to tie up a starship's sensor grid. A fighter might even be able to be outfitted with extra sharp sensors ...
Returning to the OP. The same attachment points that would mount a external torpedo, would also mount external sensor pods. It might also be possible to attach a habitat module for longer term patrols and science missions, utilizing the fighter in a small "tug" configuration.