10,000 should be plenty unless you're downloading things willy-nilly.
Outside of other creators' edits, the bulk of my downloads are custom moves with a small amount of items from Parts Craft.
I currently have 8,136 subscriptions and am not living my best restraint life 😥 Whenever I can, I try to delete moves that I know that I don't use and I am better at not subscribing in the first place. But I still have just move bloat so bad that my game will crash if I'm not careful. I know the majority of my subscriptions are moves but I also have a ton of edits I never use that I could probably easily part with.
You all laughed and mocked me when I talked about having over 7000 items and it causing the Mod Pack to take 45 minutes to load!
Anyways, this week I learned the hard way that a championship cannot change hands in an over-the-top battle royal if the final elimination is in fact an over-the-top throw. That seems counter-intuitive to the whole point of having an Over-The-Top Battle Royal AND being able to assign a championship to be defended in that match.