I do find the current setup suboptimal. Imho, DAVx5 should refresh the collections list more intelligently.
E.g. when opening the account settings, such a refresh should be done automatically for an account.
And I do find the distinction between “refresh collection list” and “sync all contacts and calender events” not obvious. I.e. why should pulling down do the former and tapping the lower right action button do the latter.