Appearance of breast implant with no breast tissue?

I had a unilateral mastectomy when I was younger for medical reasons and the asymmetry of my breasts is a huge insecurity and impacts me daily. I have about an A cup on my one side and completely flat on the other (the tiniest bit of fat and then I can feel my rib). If I were to get different sized implants to make them even, how different would they look in appearance? I want low-medium profile B/C cups that look as natural as possible. Is it realistic for them to look real and symmetrical?