The differences between WiGEs and ASFs are profound.
WiGEs are really closer to VTOLs with how the rules treat them, but they're still fundamentally different than helos.
The important characteristics of WiGEs:
They have two movement modes, along the ground and airborne. (technically, like conventional aircraft do!) They always only have 1MP on the ground and it's usually kinda pointless to use it. But they can land more or less anywhere that's open terrain for free, and it costs 5 MP to "take off". IIRC they've got the same abilities/restrictions on the ground as do hovercraft, although they also have the ability to float safely in water.
Once airborne, they always stay 1 elevation above the terrain hex. This means they need to go around things like trees and buildings. Unlike VTOLs, they can't ascend higher than that. But also unlike VTOLs, they gain elevation for free when going uphill or downhill (so long as it's no more than 1 elevation change per hex). As a fun point: they CAN go flying off a cliff (they just can't fly UP one) and "land" safely at 1 elevation above the ground as normal.
Proper aircraft on the other hand (conventional fighters, Aerospace fighters, etc) have an entirely different rules set. They don't even register on the game map; they fly OVER it.
Edit: As a point of clarity, if you weren't aware LAMs have three modes: Battlemech, ASF, and hybrid "AirMech" mode that works under the same rules as WiGEs. As I said there's no such thing as a LAM that drops the ASF, but it'd be neat to house rule one that did.