As far as cable size goes, you cannot "over amp" a cable, it just doesn't make sense for the manufacturer to use cable that is larger than necessary on a cost / weight scale.
On the other hand, you can "under amp" a cable i.e. try to pass too much current (amps) through a cable and it will catch alight ! My advise would be to try to match the cable sizes as near as possible to those that the manufacturer fitted or use slightly larger, never go for a cable that is thinner than what the manufacturer fitted as they always use the smallest cable that they can get away with.