Help with direction for new project

Starting a new project and trying to figure out how to approach the main concept so as to pick the right resources to support it. The site is going to be a dynamic group note taking app and has some key features that I think will make one database easier then the other.

• User created note templates (similar to how you can create templates with google docs) that will have set fields and spots to input data. Not entirely sure how to save the templates though, as HTML strings? Json layouts?
• Group editable notes, want note boxes in the templates where any invited user can edit it freely, assuming action cable will be used for this one.

So database is the big choice I think from the get go. Since the note pages are dynamic (depending on the template they create) and wont have a set structure, im thinking a nosql option like Firebase cloud firestore would be better. But I know rails tends to prefer a sql based database.