Propecia would work better to prevent future hair loss; that is true. It is generally pretty safe for "most" people. However, taking a pill that lowers DHT in your whole body is not the best thing to do with very minor hair loss. DHT affects a lot of things throughout your body. Propecia will also increase testosterone and your body may up the estrogen, in response. Most people get some minor side effects, like ball ache, loss of libido, watery semen. Rarely some people grow breasts. Ball ache can be annoying, but often goes away. Loss of libido would not be nice. Growing breasts, though rare, would not be nice either. So, I wouldn't touch Propecia until you see more receding and/or thinning on the top of your head(vertex). You don't even need the 2% Nizoral. The 1% is fine, used twice a week. Get some Rogaine Foam and rub it into your hairline. Rogaine halts hair loss in most people and regrows hair in a lot of people too(though those stats are for the vertex area). Exercise and supplements will do nothing to affect your hairloss. It's a genetic thing caused by the hormone DHT and follicles sensitive to DHT in people with the hairloss gene(s). Get on Nizoral and Rogaine and you will probably be fine for awhile. If it gets worse and your hairline starts receding more and your vertex starts thinning, then consider Propecia. Some people with hair loss won't even consider Propecia, because it changes your hormones. Your hair loss is extremely minor. It's normal for a lot of men to get somewhat of a receding hairline.
You might be fine doing nothing at the moment and you might not lose any more hair for many years. If you have a lot of blood relatives with early thinning hair or baldness, then you probably want to get on Rogaine. If you have no family history of male pattern baldness, then you might want to just wait and do nothing. Rogaine won't hurt you as far as side effects. It might irritate your scalp a bit, but that's it. Also, one you start either Rogaine or Propecia, it's a lifetime commitment. If Rogaine stops hair loss or regrows hair, the Rogaine dependent hairs will fall out of you stop using it. Same thing with Propecia. If you stop it, the DHT will increase and make you lose hair it prevented from falling out or regrew.