Re: Differences between female & male practitioners
You are asking good questions.
"ki" or proper use of structure and energy in aikido is NOT the same as developing the strength to muscle through techniques. There are many dojos that give lip service to softness and relaxation while in fact encouraging students to muscle through technique.
For instance, to move the new young white belt guy, applying more muscle force to make him move wouldn't be my goal because this would be training the wrong things into my body. My goal would be to find the proper structure and angles that let me take his balance. I might not always be successful in getting him to move, but it is where the training needs to be.
In terms of how you approach each student, see if you can get beyond your own gender ideas and individualize to each person's level: there are women who being athletes or working in the craft trades or simply by disposition are tough and bouncy regardless of size and there are men who are unathletic or slow or prone to easy injury because of being very stiff. One size doesn't fit all :-)