BuddyPress.org

>a page where my users can be curators and have collections of custom posts

CPs that they created ? Or created by anyone ?

Usually a profile extension is used for this.

But you say ‘outside of buddypress’ so you mean a WP page… ?
Then, because you want it driven by activity_ids, write a custom query.
Use each activity_id to find the user_id in the activity table, look for posts by that member in the posts table and show the results in a loop.
Use 2 queries if you can’t write a JOIN.