Once you have flight, and therefore fighters, Stealth is only a couple of turns away. Four or five at the most. I wait for something more powerful and maneuverable.
I don't waste time nor units on carnage or prolonged war, but rather exercise economy of force, in overwhelming proportion.
I never fight a war that takes more than one turn.
So, recon by fighters and alpine troops is somewhat of a waste of time and resources.
A transport full of spies can have a look about the place for a turn, so that I build up a picture of what is defending which city. Then swoop down with airpower, maneuver armor or mech inf next to the cities, then go into to every one in rapid succession, ignoring partisans who disappear when the civ is dead at the end of the conquest turn.
Alpine troops may bee useful for recon, but the AI has a nice habit of building a railroad network for spies to use, and they have three moves, and can look into towns. This makes them superior to a unit that is only effective against pre gunpowder opposition, and looks silly
Occupying forts and collapsing mines is for those who do not understand the true wonders of democratic blitzkrieg. War distracts you from the true purpose of the game, but when prosecuted with the right units and strategy, is a 100% guarranteed quick exercise.