Finesteride is indeed the generic of Propecia. When I was working in the pharmacy, we had a few patients on it (cisguys), and for one it was effective, and for the other two it was not. A lot of hair loss is genetic. However, for one of my patients, he developed kidney problems, rashes, and unwanted hair growth in other areas. So it is always something to keep in mind.
As for effects on T, I am not sure. I know that Rogaine is not effective for a lot of people, and with it being topical, I doubt it would affect T. I would suggest that you talk to a pharmacist and ask them about possible side effects.