The jam page states:
The best overall game, and as well the best games in each of the rating categories will be the "true winners". They will get showcased at the top of the page and on our Discord server (including a fancy role).
This means that the highest rating of all categories will be the winners. There will also be an overall winner that has the highest average rating. The only thing the jam hosts do to influence this is checking if the winner in each category has a minimum of 20 votes, if not the first next entry in that category with the highest rating that does qualify for a win (20+ votes) will be the category winner.