My advice: no one can be a girl or boy for life. Part of what pushed me into finally accepting I had to start T and accept who I am is because I was being seen as a boy at 28 years of age with already greying hair, that was just ridiculous and stupid. Even the idea of wanting to be a boy is just disturbing. Maybe not so bad if you're asexual but otherwise it's just catering to pedophiles and that's just highly disturbing! :-/ How do you honestly see yourself being "a boy" when you're 40, 50, 60 etc and you're very obviously not a teenage boy? The best way I've heard it said with regards to deciding whether to start HRT or not: do you want to grow old as a man or as a woman?
The whole idea of picking and choosing what you get from testosterone is just insane really. You get what you get, all the good with all the bad. You don't want to get bald? Tough! It's a risk and you either take it or you don't. You don't think every single guy, cis or trans, would like to able to have the choice not to go bald? You don't want facial hair: have you heard of a razor? I shaved this morning, and last I looked there were a lot of guys without facial hair walking around like regular guys!
People who dip in and out or take in low doses to try and get what parts they want are really just an insult in my opinion. Dipping in and out just wrecks and confuses your body and I don't consider it safe with regards to how it messes with you psychologically. T isn't something that should be messed with. In my opinion when you make that decision to take T you should know in your heart that you're ready to become male in a medical sense and stick with it. There are irreversible changes, it's not something to play with. Cis people can't choose. If you want to take T, then you should want to be chemically male regardless of risk of baldness, acne, reduction in life expectancy, etc. If you only want some of the changes, you're not committed to becoming chemically male and it's not right for you.
If you only want T to take away periods - do NOT take T! There's many more options for you that would suit you better.