I had an orchi some 2 years prior to my GRS.
The procedure was in the morning. I had hot flashes in the evening. They stuck around a little on day 2, but were pretty much gone by day 3.
I had transitioned 5 years prior. I didn't experience any significant additional development. But my partner and her parents tell me that my personality changed a lot afterward. I lost a lot of anxiety and was able to toss my mood stabilizers.
Also, a funny little detail that makes sense in light of the anxiety -- before the orchi, my eyebrow twitched when I was stressed. Afterward, no twitchy.
The big thing that I hadn't expected was the nature of the swelling and the time it took to dissipate. After an orchiectomy, there is some generalized swelling throughout the area, but the main things that will annoy you for months are the ligated cords. Immediately after the procedure, the cord-ends swell up with blood and fluid. They congeal and harden to little lumps that feel disturbingly like the organs you pay the doctor to remove.
YMMV, but generally they take months to go away. For the first few weeks, they were the size of walnuts. By the second month they were the size of almonds. By the third month they were the size of raisins. And then they were gone.
This process then repeated itself when I had my GRS, because my surgeon had to "clean things up". The doctor who did my orchiectomy was kind of sloppy with his ligation and moreover did not use dissolvable sutures. That made sense, because I felt them moving around and causing occasional pain for the years between procedures.
Either way, I healed fine from the orchi, and it didn't affect my GRS other than some extra time under anesthesia.
I was disturbed in retrospect. I felt lucky to have such a minor problem. I knew the guy who did my orchi was kind of batty, but I went ahead with it anyway.
Why? Because my old out of state driver's license was expiring, and I had run into a brick wall trying to get an F on my license without having had surgery. I preferred the batty doctor to the M.