I think there are no guarantees (about anything in life, really), but that any experienced surgeon is likely to do good work and produce a result that will be functionally and anatomically within the range of cis vulvas. That range is pretty large, too.

One reason I think people say that it can't look cis is that they don't realize just *how* much variation there is in cis women; there are cis women who've had surgery or have scars from childbirth, women born with no inner labia, women with large/small clits, etc.
I can't promise anything either, obviously, but the GRS results I've seen in person have been perfectly normal-looking, and the owners reported that they worked fine. (As for myself, I had a gynecologist who wrote an official report that I was a cis woman with a hysterectomy, and then she argued with me when I called to get her to fix it!)
Don't worry too much if it looks really weird at first, either. Healing can take many months, and the interim stages are not necessarily that appealing.