You can both compete in all races and challenges, with the exception of boss races. (n64today.com)
For example, Diddy Kong Racing features novel boss races in which you must beat one of the island's creatures across the finish line. (n64today.com)
The career mode also impressed me by having more than just your typical races: it even featured events such as slalom (the classic Wave Race mode in which you need to move left and right through gates) and boss races which reminded me of the good old Diddy Kong Racing. (waytoomany.games)