I generally try to keep the lore sensible and not force players to suspend their disbelief too hard. This is why I try to keep a lot of LORE reasonable and expand it as the story progresses. Sexual dynamic in the setting is one of these things!
Generally speaking, what I said above still applies; it largely depends on the species, on a planet, or even on a specific city, tribe, space station, etc. Around the Periphery, the sexual dynamic reflects pretty much its politics; it's largely completely free for all, where everyone does everyone. SP is a futa on femboy game. Hence, most of the stuff you get to see is futa on femboy. But there most certainly are futas who are into a different kind of love. For some, it's the novelty of things (i.e., big blue ladies not having males, hence feminine human males are especially pleasing and attractive to them) or the dominance/status aspect, like for the orc ladies. You can read the alien sheets for more!
Regarding procreation, a similar applies; for the blue ladies, they can make offspring with their own females (and they are also compatible with humans; you'll meet some half-tarnians later). The Pyrphera, on the other hand, are mono-gendered and procreate with a certain kind of flora of their home planet, and sex with other species is generally based on pleasure or as a transaction. Gobbos are very compatible with nearly every other sentient species, too. As I will be unveiling more species, more sheets will follow, and you'll get more information about the topic as well! I also plan to have these basics in the upcoming Codes (which will be coming with the UI rework sometime around R7)!
Yes, there will be both human and alien femboys!