I can only comment on my own experience. At the time of my right breast mastectomy 2 sentinel nodes ( positive) and 5 ( negative) above it were removed. It caused numbing under the arm and a bit down the underside of my arm because nerves are severed. Over months a good bit of feeling has returned and is still returning. I did not experience lymphedema but I understand that can happen even years after dissections. There are lymphatic massages that trained physical therapists can perform and also ones that one can do oneself.

I did have two drains installed at the time of the surgery and one was there for two and the other three weeks. I always assumed it was for the mastectomy verses the dissection but perhaps it was for both.

Looking back will not serve your needs right now. We do the best we can with the information we have at any given time. Save your energy for the decisions that you need to make right now.
Blessings. 🌸