[Knufire]

Are you looking for different powertrain options (number of motors, shifting vs no shifting, number and type of wheels) or different frame options? The AM14U3 is configurable; while there's the single configuration that is supported out of the box, you can purchase additional wheels, pulleys, belts, and gearboxes from AndyMark to add additional motors, shifting, or change to a number of wheel configurations. Picking these are typically based on desired performance characteristics of the drivetrain based on the game.

However, frame type (KoP, 2x1" WCD Frame, Sheet Metal, Plate Drive, etc) is something I typically like to consider separately. They all have their advantages and disadvantages performance-wise, in terms of ease of mounting superstructure, modifications for a large angle of attack for obstacles, etc, however, I think the overriding factor in choosing a frame type is your team's manufacturing resources and what would be easiest for your team to manufacture.