Hair works for all figures.  Just use the scale dials to adjust the size and the Trans dials to adjust the position.

Poses work for all figures. Sometimes you will need to adjust an arm or other major joint like a hip or shoulder and sometimes the fingers, but M3 poses can be used on Aiko and Aiko poses used on Mil Baby if you want, etc.

Clothing is not so easy.  It's pretty figure specific actually.  However, if you have a program like Wardrobe Wizard you can convert clothing from one figure to fit another figure, provided Wardrobe Wizard supports those 2 figures.  For example you can convert a clothing item from Aiko to fit The Freak, or Apollo, or a morphed V3 or even Laura. etc.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi