Hi Allie,
Thank you so much for your honest post. This is where a forum like this can come into its own.
This may not be a popular message but I would go against those who urge you to proceed. If you have this much confusion then I don't believe having highly invasive life-changing body-altering surgery is going to be your panacea. It simply isn't, though this is a common mistake in this community. You need to see someone professional and very, very, good in my opinion to talk through where you are at. If you can say which country you are in, then I might be able to give you a steer.
Re. the orchiectomy, whilst it's true that this is much less invasive it's still life-changing and body-altering. You will never get back your testicles, nor your ability to reproduce. It's an operation which may leave you feeling somewhat neutral which can be positive, but also disorienting. You will still have your penis, a bulge (albeit smaller) and look down to male genitalia. These are psychologically significant points. Hormonally, though, you will be entirely non-male. As you say, your testosterone will vanish entirely. Assuming you take some oestrogen, which you will need to in order to prevent osteoporosis, then you will be hormonally female. You will probably lose most function down below though it sounds as if this will be less vital to you. Your prostate is still a powerful gland and can produce ejaculate.
I tend to think of an orchiectomy as a staging post: a launch pad for the next phase. There are some exceptions to this, but generally it's the case that it's a half-way house. As such, it may help you to experience it in terms of then preparing yourself for the bigger operation to come. But only if you are absolutely sure about not wanting to be male because effectively that's what will happen with the orchie, albeit retaining your main male member.
My advice? Please seek some further therapy if you can from someone really good and empathetic. Talk through all these issues, including your fears regarding surgery, but most importantly about your gender identity. If you are really truly sure you want to be female then presumably vaginoplasty is the way ahead? When you are ready.
Hugs
x