Honestly, if you are starting hormones at 17, you have a lot of advantage to someone like myself who started at 28. Muscles and skin will be affected by the hormones over time, and I have found that most trans-women have a reduction in muscle mass and softer skin after even a short time on hormones. I was convinced i wouldn't pass when I started, and now a year later I would have a lot of trouble passing for male. I have seen many cases where I have thought that someone pre-transition might have problems, only to see them be accepted completely as female later. Starting young is a big advantage.
A friend of mine told me that a lot passing is from the neck up. Some things like excessive height and broad shoulders can be a hinderance, and cause problems, but I have not seen anyone outed for having muscular legs. (if fact , some of the GG's I know would have a lot to worry about if that were true.)
At 17, those hormones are going to do a heck of a lot to you, and I would be surprised (shocked really) if you didn't pass completely after a year on hormones (or less).
keep educating yourself, and asking questions. It's god to hear that you discovered yourself so young.
Hugs
Mila