Thanks Paul - yes indeed - Quill is best for clean, simple HTML so anything that needs to be edited on the Notes client should be left with the RichText editor. For tables, plugins like quill-better-table extend the functionality and pasting formatted HTML is not bad but haven't experimented with really complex cases. What's nice about Quill is the extensibility with all the various modules available.
Are you aware of any plans to upgrade the built-in RichText CKEditor in XPages? (wishful thinking!).