I am short on answers but have a lot of questions. The answer you supply might make a lot of difference in the value of answers you get later.
We hear from people who have had problems with propecia and while your result is not all that common, it is not rare either. If the breasts became enlarged and increasingly tender, How long had you been taking the drug before you noticed that effect? How long has it been since you stopped taking the drug?
Swelling and increased tenderness are not necessarily tissue growth. If the offending drug is withdrawn soon enough, that swelling and tenderness may diminish without treatment although it is a slow process. If actual glandular tissue growth has occurred, you might not be completely certain for a year or even two. If the breast size has not diminished in that time it most likely will not diminish and surgery is the only treatment.
Your question regarding Pseudo-Gynecomastia vs True Gynecomastia is common enough. As the work "Gynecomastia" is commonly used these days it refers to any surplus of tissue in the breast area of a male. The older terms of Pseudo Gynecomastia as breast enlargement that is entirely fat and true Gynecomastia which is entirely glandular tissue; simply are out of date. It would be rare to have only fatty or glandular tissue. the usual situation is to find a mound of fatty tissue with threads of glandular tissue through it. In any case, since surgery is the treatment either way so the old distinctions really make no sense. The breast area is one of the first places where a man will put on fat and one of the last places where he will lose it so weight loss might reduce the breast fullness some it will not get ridof them.
As to the surgeon. We occasionally hear of stories where a person got really good results from a general surgeon but horror stories are more common. If you are going to have surgery, I think it would be wise to hold out for a cosmetic surgeon and one who does this kind of procedure often.
If, in the short term, you want to conceal the condition; There are several compression garments that can be of great help.
Good luck and welcome to the forum.