Does a 'Mech Battalion act "en masse"? That's basically what you are asking. It depends on the need of the mission. Some missions need a battalion, some need a company, some need a lance.
I have no problem with 'Mech Battalions but Aerospace Fighters are a little more complex to use.
Oh? How so?
Lets' take a hypothetical case where a wing might see action.
The Federated Suns is carrying out a regiment-size raid into the Capellan Confederation. For this purpose they are using the 1st Federated Suns Armoured Cavalry: one 'Mech regiment of 112 (4+(3*36)) 'Mechs carried on 2 overlords, 3 Unions and a single Leopard; one aerospace wing of 20 (2+(3*6)) ASF which conveniently fill the aerospace bay on those 'Mech transports; and two tank battalions aboard a pair of Triumph dropships.
They jump in at a pirate point, leave their jumpships there to recharge and the dropships make a run to the target planet. During the run, the ASF squadrons rotate ready-status so that one is always ready to launch in case of trouble but the most likely time for interception is as they reach orbit (when the dropships are moving slowest) so the entire wing launches to provide cover for the orbit-to-surface phase. During this period their focus is interception of Capellan ASF before they can attack the dropships.
So the Mech transports drop the 'Mech regiment over the target (probably at least a squadron of ASF will be escorting them down) and then all the dropships come down to land at the extraction zone, deploying the two tank battalions to protect them against ground attack. The ASF land once they're down, refuel and reload. From here they go back to squadron rotation: one squadron making repairs to armour and so forth, one ready to launch to provide air cover to the dropships, one in the air with individual lances doing recon, covering the Mechs and bombing targets of opportunity as the situation demands.
The Mechs hit the target, pick up what salvage they can and head back to the dropships. If the situation is really good then they might hold the target with 2 battalions and send the other back to the dropships to escort heavy trucks back to the target to pick up heavy salvage. Once everyone's back and loaded, the dropships head back into orbit, escorted by the aero-wing, and then burn for their jumpships. Once they pick up enough speed the aerowing can have a couple of days rest before they cover the dropships while they dock with the jumpships (the last vulnerable phase of the operation).
So in this op, there's likelihood of space clashes involving anything from an air lance to a full wing, squadron clashes covering the dropships from being bombed and the dropping Mechs from being picked up before they hit the dirt and lance clashes as they hit targets of opportunity and try to obtain or deny recon data. So the forces used depend on the situation but fighters aren't really more complex than Mechs.