I was going to attempt to hand write the addresses on our envelopes based on traditional etiquette and the fact that my writing is quite nice. But we chose the invitations below which offer an "address label wrap:" the label wraps around the envelope with our return address on the right side of the back and the guest's address on the front. As shown in the 4th picture of the link:
https://www.etsy.com/listing/91903981/contemporary-triple-striped-modern?ref=favs_view_16
FI is OBSESSED with the labels and thinks they make the invitation,
So, to label or not to label?