I've done a fair amount of research on orchiectomy because I hope to have one someday. A couple of things I keep reading:
1. Some SRS surgeons won't touch you if you've had one. Others don't care. Still others don't mind as long as either they did the orchi themselves, or know that it was done in such a way that they can work with it. My impression is that, if you hope to have SRS one day, it's best to establish a relationship with that surgeon BEFORE getting an orchi. If you don't, you could find your options limited later. If you can't establish such a relationship, and you feel that you really still need to go ahead with it, make sure that your orchi surgeon knows what your later hopes/plans are, and has expertise with transwomen and the special needs of someone who may undergo SRS one day. They are out there, but they are the minority. (Orchi is far more common as a treatment for testicular cancer, and things like the location of incisions don't matter at all in those instances.)
2. It's not a guarantee that your scrotal sack will shrink after orchi. YMMV, and some post-orchi transwomen say that shrinkage is a total myth. As reported above, if you do start to see shrinkage, stretching can make a world of difference.
3. Orchi is MUCH CHEAPER than SRS -- in some cases one tenth the cost or even less. Money is always a big factor in transition, but your orchi is unlikely to be your largest expense, or even close to it. You may very well spend more on electrolysis. And the cost is offset, at least partially, by a reduction in what you will spend on hormones. Do the math, and you may find that it pays for itself.
4. The vast majority of girls who have had one report that the benefits to orchiectomy are immediate, permanent and wonderful. Your hormone regimen can change immediately, and the feminizing effects grow. But there's really no turning back. It is a minor surgery, but not to be done lightly.
I'm not really trying to sway you. Just trying to summarize what I keep reading.
The most important thing, like all aspect of transition, is to consult with the experts before you do anything. Make a long-term plan, with the help of the professionals, and then implement it. Understand the risks and benefits thoroughly, and don't make decisions without knowing all of the potential benefits as well as the potential consequences.
Good luck!
Lora