Norwood scale describes baldness and it's commonly used as NW#. Below you got one of the many illustrations of it:
So NW5+ means that you can go to the situation marked as V on the pic or even worse. It may never happen, but diffuse thinning all over your head indicates that.
Propecia/Finasteride is for now the most efficient treatment available and because of that it's important to see if it works for you. There cases reporting negative side effects (impotency, male boobs...) and other claiming fin doesn't work at all, which is statistically totally possible - it "works"(stops hairloss at current level or even inspirates hair growth) in about 2/3 of cases. Therefore it is important if it works for you, because if it doesn't you're bound to lose the remaining hair. That's why I somewhat doubt in your doctor's ethics because he didn't warn you about that. And it's kinda common belief that hair transplants are riskier before 30s. A good candidate under 30 years would have to be on Fin for at least couple of years to see if it works and the hairloss is stopped or at least heavily reduced.
This is also where my second concern derives from - FUE/FUT. FUE indeed costs more, takes more time and cannot yield as much grafts as strip. On the other side it is great for smaller sessions like 1000 - 3000 grafts, while strip yields great results even with megasessions like 4000+ grafts. Since you're most likely bound to have at least one more HT it would be wise to "use" that scar you'll be left with in any case for a larger number of grafts. You have a scar, so why not get as many grafts as possible for a price of a smiley face from ear to ear on the back of your head.
About being dependant on chemicals - that's one thing you have to take into an account when having a HT, especially if you're 27 yrs old with progressive thinning. Because without them, you'll turn into a regular at HT doctor's surgery...
5 years ago I almost scheduled for a HT with a presumably excellent plastic surgeon who did a lot of work on local celebrities but I somehow didn't take that step. I'm bloody thankfull to myself I didn't do it, because from what I've learned in the meantime I came to realize he was a regular quack at HTs although he apparently does great job concerning plastic surgery in general. And reading some forum testimonials of his patients just confirmed my suspicions.
Now I'm reasonably educated about hair transplants and I wouldn't let anyone but few top docs touch my scalp even though that would cost 3-4 times more than with the above mentioned docs. And since there are quite some hairloss forums the names of the docs with good to excellent results keep being mentioned - Bisanga, H&W, Umar, SMG... and on the other side butchers like Norton, Bosley etc. I believe there are also a lot of average HT doctors who don't get mentioned at all and you can also get a decent result there, just the chance of it is smaller than with top docs.
I wish you all the best, what's done is done. I don't want to put you in the bad mood, but the truth is that is a lot of quacks in HT business and that's why you are the one who has to make a research on what option to pick. And never I repeat - never spare your money on hair transplant. It's better to be bald than have some crappy job on your head... I think quite some few forum members will agree with this...