Hoppers seem to be some kind of air transport; in "Nor the Battle to the Strong" we hear about plans to evacuate over 70 patients, most of whom were laid down, and at around 10 doctors. It was also stated that Starfleet is sending security detail to defend hospital and give them time to evacuate, so it is possible that hopper could hold at least 150 people, maybe even 200.
Also, soldier in that same episode made reference to hopper his platoon was boarding. Platoon, in modern classification, is usually 26 to 55 people. He also mentioned that he stayed behind to provide covering fire, which implies that "hopper" is lightly armored and armed. Also, both its usage and name imply that hopper is relatively short-range atmospheric craft, possibly Federation equivalent of modern Blackhawk or, more likely, Chinook.
No other specialized aircraft was seen or heard about in Federation inventory, however Federation Attack Fighter (seen below) can be useful in direct fire support role.
It is armed (according to Memory Alpha) with 3 torpedo launchers, and 2 phaser emitters (one emitter in nose, firing beams, and two more at end of each wing, firing pulses).
