I saw no effect in the latter case, at least nothing worth risking the pilots for. Perhaps the Maquis surprised Evek pants, I mean shields, down, like they did the Malinche?
On the other hand, the Maquis that hurt Evek (but failed to destroy his ship) were said to be sporting Type 8 phasers, hardware canonically associated with the Enterprise-B, if only in an Okudagram. And supposed Cardassian small/medium craft later sported "Galor class" phaser banks. So rigging a capital ship gun onto a much smaller vessel might be possible after all.
I'm inclined to think both cases are likely myself, that the Maquis ambushed Evek's ship and we see the Enterprise responding to that ambush at the beginning of the episode. I seem to recall mention of the Cardassian dissidents getting their hands on Galor type weapons, so one could say the odds would have been relatively even from their perspective.
A single phaser emitter in turn can vary in power, and those on the runabouts or the small Maquis ships were shown to be fairly impotent even against other small craft. We have no idea about the size of a phaser gun onboard a capital ship, except for minimum estimates based on visible components; the ones on a Galaxy are the size of small villages.
Perhaps the difference might not necessarily be size, but the range of power that can be pumped through the emitter? It's logical that a capital ship would be able to pump more power into its weapons, and I've read about the Galaxy's collimated array having the main advantage of much better arc coverage than the older phaser mounts. The design of the phasers themselves wasn't necessarily more advanced or powerful, by a huge margin at least, but it was more flexible and allowed that power to be applied in a more forceful manner than the point defense configuration.