For an app like Notion you don't have direct peer-to-peer syncing: you have a star topology with a central service able to create a canonical total ordering of events, so you really don't need CRDTs at all.
Direct peer-to-peer without a intermediating server is so rare for SaaS that I don't even know of an example.
When inserting text, you can either use mutations that insert the text relative to some reference character(s) or at some index. The former is basically the approach of most text CRDTs. I'm having a hard time imagining the latter without modifying the insertion index relative to concurrent insertions or deletions. I believe that Jupiter based OT imposes a global order, but uses it to determine how concurrent mutations are transformed against one another.