May I ask what's the limitation of Category items in RTC?

I should mention that any item such a categories need to be loaded before they can be selected in the UI and in IT size does matter. The more you have of categories/team areas/enumeration literals/http filtered values/links/whatever item, the longer the load. Over the last years some of these items have been added to the cache, so only an initial load is involved. In general size matters but not in the direction you express in your question.

Thanks for your detailed explanation!