OK so I've trained all walks of female BB up to the pro level. At the pro level unless I would see something total wrong or outrageous I would normally won't touch anything. These girls have been on for years and generally know how they affect them and are past the point that they are worried about their femininity.
Now, I have had a lot of girls who were totally natty that have come to me and I have never ever suggested steroid use to them. It's a different story with women. I would never suggest that a man take female hormones to the degree that it would change their sex either. I see a lot of "gurus" who are putting bikini competitors on drugs and I can't fucking believe it!!!! Why in the hell would you put a bikini competitor on Anavar DNP and T3?
I don't feel that there really is a sweet spot so to speak. All you can do is try to minimize the side effects relative to the degree of muscle mass you are trying to achieve!! READ THAT AGAIN!!!
I hate to name actual compounds but here's my opinion only.
Anavar is one of the worst drugs for a woman to use. Within 10 days their voice will change. I seen better results with Winstrol at around 5 to 10 mgs on first timers with no voice change and little to none masculinization effects.
I know a woman who was prescribed a low dose test patch and she got some good results no voice change but I certainly would not like to see a woman injecting test.
This one may shock some of you but Anadrol at very low dose (10 to 15 mgs) will have a good effect on building muscle with little to no side effects.
Very short term oral and injects with experienced users is what I think should be used. That way if sides show up can pull it and take some Aldactone and you should be fine.
As far as length well I think that doing short bursts with some time off is best. Build some muscle back off then hit it again. Hope I covered all of your questions.