No right or wrong. Also depends on family traditions. When my bf proposed with ring, I considered us engaged. We didn't have an engagement party. Of course my parents era didn't have this "engaged" business. Their era, they went straight to the ROM.
I still refer to my fiancé as my bf sometimes. Other times I refer to him as my fiancé. Depends who I am talking to and what term I felt like using at that time.
So it all depends on how traditional and particular u are.