@GuoJing Welcome to the community.
Team is working on updating collection and set, so there should be some improvements.
Your concerns over relation are shared by fellow community members. You might want to add your ideas in the following posts:
- Add support for collection-specific relations
- Change relation type
- Merge feature for relations
- Something like Disambiguators but for relation
As for notion, from what team has demonstrated so far, Notion is a big competitor to Anytype and a major reference for them, but some things require more efforts to be implemented in offline environment. After all, Anytype is still in beta and Notion is a well funded mature application.