don't over think it, use your cheaper road shorts as a liner. Chamois quality less important IMO for mtb. I actually don't like cargo shorts as they are typically too thick and bulky. Though I've found lightweight hiking/fishing shorts fit better for me when riding. Regular cargo shorts tend to larger leg "holes" which get in the way or maybe it's just my stick legs.... Like PickleRick mentioned, I'm never buying any other pair of mtb shorts with the built in liners.