With the Minthara scene you very specifically have the option to take charge (with a fairly tough persuasion check) . I may have a save in the camp celebration to test it out later. If so I'll let you know.
So I tested a few combos and there are some interesting dynamics with f/f Minthara.
Spoilers for pg-13 descriptions of things
First, you can just jump right into it and she starts off pleasing you and then climbing up for a 69 which leads to cuddles and a check to read her mind's desires or fears.
Second, you can persuade her to submit to you DC 20 and it seems to lock out all spell bonuses, so it is just CHA and Prof if you have it. In this case you push her back and climb on but it is interestingly a little more romantic of a scene, with some gentle spooning before she climbs on top of you.
Either way, you can then read her mind and either delve into her desires, which will make it easy to convince her to join you. Or you can read her fears which will then require an intimidation check DC 15 to make her agree to let you live
