I use registrations for most all of my song styles. Save the reg with the harmony on, then save the next reg with the harmony off.
I also use the Registration method.
I have slot #1 set up with the mic completely OFF (no sound at all).
Slot #2 is set up with No Reverb on the mic and the volume turned way up high. I use it to TALK to the audience, it makes it easy to get their attention.
Then at the other end of the Registration I have Slot #7 set up with just my voice and No Backup singer with about 17% reverb added (you got to have a bit on your mic).
Slot #8 has the Backup Singer with my Voice (again with reverb).
I have over 30 different settings. Some with one singer as backup, two singers as backup, some are with men others have women. Then some have 17%, 25%, 40% and 50% of Reverb on the mic, it all depends on the song.
A few setups use a third slot #6, there I use the Voice Doubler or the Male to Female harmony.
I always take the time to setup a custom style for each song to perform each tune. I never use a registration for that task, except in rare situations.
Regards
Drake