> Plan to have user data stored in plain files as well.
That would be cool :)
> such that it's quite fast thereafter
Not always :) I saw that myself and I also see complaints on Roam Slack. In my experience it mostly depends on how many queries you have on given page, but sometimes it lags (long waiting time when switching between pages or opening note in sidebar) also with simple, "atomic" notes. But they overall struggle with polishing existing parts before adding new features, so maybe performance is still on its early days in Roam.
Anyway, I wish you good luck with your project :)