AT-RT is based on the idea of using a motorcycle frame for the correct posture and feelings from the vehicle.
Let’s be honest, AT-RT is literally a dirt bike on the legs :)

It’s a minifig scale.
The height should be 3,2m according to Wookipedia, so ~2 clones’ heights.

Legs are posable, and pistons under the seat are really connected to the legs.
The reference was the AT-RT from Hot-Toys

Parts purchasing suggestions:

11402a is usually cheaper to buy in 11402 together with other tools.
50018e and 50018c are cheaper if you buy them together in 50018. You will need 2 50018 elements
48729b or alternatives should be used in light bluish-grey or dark bluish-grey color, as these colors provide the sturdiest joint connections.
44 price-color correlation is related to region, so feel free to use dark bluish-grey or blue, if they are cheaper in your region