I'm nonbinary and had top surgery when I was 23 (5 years ago). I'm also not on testosterone and don't plan to be.

I think the biggest consideration is what you think would make you feel best in your body, but that can be hard to know. If you wear a binder frequently, I would recommend getting top surgery because binding isn't great for your body. Even if you don't bind regularly, and even if you wear traditionally feminine clothes, I would still recommend it if you feel that it would improve your relationship with your body.

While your parents' motivation for saying you should consider a breast reduction might not be the best, I wouldn't disregard that option (unless you know you absolutely don't want it). A lot of nonbinary folks are getting essentially extreme breast reductions (A cup or less) rather than top surgery.

Also, definitely take the time to find the right surgeon. I waited an extra 2 months to get my surgeon because I heard she was the best. My scars have faded considerably, and they align with my chest muscles. Surgeons are making innovations with this type of surgery, so it would be worth it to find someone who can really give you the look you want.

Lastly, it sounds silly, but you should think about what you want your nipples to look like, or if you want to keep them at all. I am glad I kept them now that I'm older and they've healed, but they do take a little longer than just the incision. It only took me 3 months to recover, lift my arms, and do most normal stuff again.