My opinion's from my life of experiences and observations:
1. I've heard stallions are much more difficult and free spirited then geldings. Will having sex with the animal help you remain in control?
2. Can it give you an edge, like helping to deflect toward a more constructive outlet?
Stallions and mares require more stimuli than most of their gelding counterparts. Sex should never be approached or thought of as something that will give you an "edge" or control in any relationship. Human or non human. Stallions do get the post sex blues like male humans but it lasts for minutes not days and is not effective in calming him down over a long period of time. Ways i suggest to get "control" are the actual constructive outlets you mentioned working towards. There are tons of recourses out there on equine enrichment. Search for things like emotional horsemanship, reward based training, and liberty training. These will help you and your equine partner gain trust and form a bond in which you can mutually respect one another. Once a relationship and boundaries are formed respective sex will follow.
Thank you for your perspective on this question, I was brought up to believe that domesticated animals were property to be cherished as a family heirloom, but like that family heirloom, it came with me and was presented the way "I" saw fit. It took me many years to realize this flawed, so forgive my use of the word "control", the animal deserves better then that obsolete thought process. It is something I'm still working on and am getting closer to being ready for what society would call "ownership," but for me will be friendship and maybe have it turn romantic depending on our bond. I will be looking into those resources you mentioned about emotional horsemanship, reward based training, and liberty training. I took a peek at all of these training methods to see what they were about and that sounds like it's right up my alley.
3. What are some examples of how sex with the animal changed that animals relationship with you in ways you did not expect? Positive and negative responses are welcome.
(note my relationship with my stallion is more of a best friend than lover) We share mares in threesomes and sometimes we have a passionate jerking session or some oral but we don't have actual sex with each other. So the following is more directed towards my mares.
For me the way sex changes a relationship with a horse is similar to how it can change a relationship with any romantic partner. Its tough for me to put up boundaries any longer between human and animals. Everything I feel I can relate to the horse. That being said sex for me intensifies the love I have for that horse. It connects us on a more primal and emotional level. We literally can feel each other from the inside, we are connected. Sex is so special and it should be treated so. Not just something to get off at, something to deeply connect over.