Thanks.
While the primary meaning of 'marcher' is 'to walk', it can be used for machines and vehicles indeed. 'Rouler' is for vehicles only. Interestingly in English the verb 'to run' is used, suggesting higher speed.
The expression “to work better” is quite common but I don't remember seeing “to work less well”. And as I was taught that « plus grand » translates to “taller” but « moins grand » to “not as tall as”, I expected something more involved.