I would use the advanced search and see which threads you can turn up. This topic has been addressed a number of times over the years.
Regardless of age, very few guys don't get much of a voice drop on T, and even if your voice doesn't drop ALL that much, you should masculinize over time so that people have no doubt about you. Some guys take longer than others.
I used to pass a lot when I was younger, and then my age and my unhappiness caught up with me, and it didn't happen so much when I was well into my thirties and then my forties--I didn't look like an adolescent boy anymore, and I gained quite a bit of weight.
When I finally decided to transition at 46, I lost a lot of weight, went on T, and had top surgery. Now I don't have any trouble being read as male. None at all. It took me only a few months, but I suspect that I was one of the luckier ones; some guys around here (closer to your age) are a couple of years on T and aren't read as male 100% of the time. But two years is a drop in the bucket if you think about it. So some guys are already read as male and T just adds to that. Some guys take six months, some guys take a couple of years. We are a diverse bunch in that respect.
I wish I'd transitioned at your age, but there was too much working against me. I simply wasn't ready. If you are, then you are at a great age for transition--and a great time, since trans people have been getting better and better resources.
Poke around the site and see what you find.