This is something of a hot topic among people interested in the Good Folk, so I thought I might as well express an opinion on it. I've already written about Sex and Love in the Otherworld, so this isn't going to be that aspect of things but the broader ideas of sexuality and gender, as I'm familiar with them in the context of the Otherworld.
For some background, we have quite a bit of folklore about the Good Folk and both gender and sexuality - my personal experiences confirm some of that folklore in some ways and may contradict some of it in other places. For a deeper background into the more provable or documented aspects of this subject I suggest my article "Sexuality and Gender Among the Good Neighbours". What follows here is not confirmable and represents only my own experiences.
Sexuality - My own perceptions of sexuality among the Good Folk is that there is a wide range of expressions, wider perhaps than the human world usually embraces. I might loosely categorize the bulk of it as omnisexual, with the only real vital factor relating to consent and ability to consent. My personal observations have been that while the Othercrowd have a very different idea of what consent is they do require it as a prerequisite for most everything. As long as the parties involved are capable of consent and have given it then everything else is a possibility so to speak. Sex is treated as both extremely sacred and also something that should be enjoyed and celebrated frequently and enthusiastically (the enthusiasm is an important aspect) by those who wish to do so.
Consent - speaking of consent, we may as well sidestep into that for a moment. So I say that in my experience consent with the Other is different than the human concept and that's actually a really critical thing to understand. The modern human understanding of consent is that it should be freely given and can be retracted at any time under any circumstances. The Other concept is rooted in agreeing to a thing and being held to that agreement - and if you agree under duress or perforce, through extortion or under threat, you are agreeing and its the agreement that matters. In the same way once that agreement is given it is not retractable in the same way that human consent is supposed to be. In order for consent to be withdrawn with the Other both parties must agree or must renegotiate the original agreement. If this sounds very contractual it is. Its also why I always caution people about dealing with the Good Folk.
Gender - Gender among the Good Folk is an interesting concept in my experience. I have encountered beings that are very clearly and strongly gendered and for whom that gender seems to be an intrinsic aspect of their identity, as well as beings who are fluid in their gender and impossible to pin down or even define. I've encountered at least one being whose gender is best described as that of a plant. What makes this subject more nuanced in my opinion is that the ones that are very strongly gendered may also be the most enthusiastic at overthrowing or contradicting gender roles in the contemporary human culture around them.
Relationships - while we are here we may as well also touch on relationship structures. I have seen some examples of what we might call polyamory, more of open relationships (two committed partners who also take other casual partners), many who simply enjoy whatever sexual experiences they can get but don't have romantic relationships, monogamy, and those who seem to have no interest in sexual or romantic relationships at all. Monogamous relationships are very strictly monogamous from what I have observed, probably because it involves oaths which the partners lose honour by violating. Friendship is of course also a common relationship.
Ultimately its a very complex subject, with a lot of layers and nuances. I can only really touch on a small part of it here, but I hope that this helps with a wider understanding or at least a starting place. And as always other people may have different opinions or experiences with this, what I'm writing here is just my own observations.