Hey, i haven’t had mine yet, so can’t help about the day case situation, but unders are if you don’t have enough breast tissue, so they put the implant under the muscle. They give a more natural look, so if you have enough tissue you will be able to have the implant over the muscle which can give a more fake look i think if you have a big implant. I’ve seen pics, they do look pretty natural to me but maybe you can ask for a more rounded look. I’m sure i’ve heard about extra high profile implants.
Good luck hun, hope the time goes quick, i’ve got to wait til June for mine, seems a life time away!!