Photo Competition with Categories

I'd like to set up a competition with multiple categories, with max one entry per category, is the best way to do this by creating multiple separate photo contests?

Yes, you have to create a contest per category.

You could create a thank you page or use the description to link to the next/other categories. We will implement a category feature in the future.

Feature Release: »Submission Categories«

When creating a Video, Music, or Photo Contest, you can now add custom submission categories. These categories allow you to divide your contest into different themes or genres. Participants select a category when uploading their entries, and submissions compete only within their chosen category.

You can easily configure this in the first step when creating your contest.