The Google account is still there, I’ve just hidden each of those calendars. New events seem to default to whichever calendar you used last (citation needed) so once you’ve created an event under the NextCloud account, it should default to that. The app I use (Business Calendar Pro) doesn’t even give the option if a particular calendar is disabled.

As far as DAVx^5^, the default is to only sync every 4 hours. Phone to NC is instant (once DAVx sees the change), but NC to Phone has a delay. However!..

I just set up the ntfy app to create instant two way sync both ways. It’s pretty slick. Dig around in the DAVx^5^ documentation about how that works. You install the DAV Push app on the NC server, ntfy on your phone, enable UnifiedPush in the DAVx settings, do a little dance, and then NC notifies DAVx every time there’s a change.