Q. How do I switch between DVD-RW modes?
A.
Initially blank DVD-RW media is in Sequential mode. To format for Restricted Overwrite invoke 'dvd+rw-format /dev/scdN'. Once the media is formatted you don't have to reformat it to zap the content, it's more than enough to simply write over the existing data [with growisofs -Z ...]. Your unit might report some bogus media capacity (e.g. Pioneer DVR-x05 reports ~8GB or 178.5% of real capacity) right after initial format. It apparently just does so till you burn some data on it, so don't get fixated on this...
To change [back] to Sequential mode [or to reuse the media in Sequential mode for a new dataset] invoke 'dvd+rw-format -blank /dev/scdN'. Unfortunately specification requires lengthy, an hour per 1x media, -blank=full procedure applied before you can reuse the media for Incremental Sequential (but apparently not for Disk-at-once) recording. I really fail to understand why does it have to be that way, but that's the way it is. Period.