Hey Steven,
Good question! I'd be interested to hear others' thoughts on this too.
When it comes to categories, I think as long as there's no keyword cannibalisation taking place and users can still easily find what they're looking for within 1 or 2 clicks from the homepage, there's not too much of an issue with creating them. But it could affect how many of your product pages get indexed, as crawlers might use their resource indexing your categories instead. That might not be the case or 100% correct, but it's something to bear in mind.
As long as your categories are logical, make sense to the end user and don't overlap with other categories much, you should be fine.
