Hi. The area of loss is not Norwood 3 or 4, it's a diffused Norwood 5. Quite likely heading towards Norwood 6. No ethical doctor would operate on you right now without you taking any medications, as you're only 21, and a lot of hair loss is still left. Rushing to a hair transplant right now would be a bad idea. The best course of action would be to get on a DHT blocker (finasteride, dutasteride) and minoxidil. Give it at least 1 year, you might make a decent recovery. The meds also might only stabilize your loss, which is a win also. It's the best course of action right now. Can't really comment on the topical mix of finasteride/minoxidil, as I use oral finasteride and topical minoxidil separately. Don't delay the meds, get on them ASAP.
Good luck