Having maximum of 10 tags regardless of premium or not feels limited, especially for those paying for premium subscription.
With a lot of tags to choose from, I feel like there should be more options for people to choose, so they can see more what they're into.
As for custom tags, they should still count towards the total tags.
I want to say for premium users, they can have up to 20 or 30 tags. Free users can have up to 15 tags.