For me, NBE was very helpful for finding a way to see if I really wanted to do HRT without needing a doctor's note etc. first, but once I had confirmed the results of the experiment, I stopped NBE and told my wife I am trans. I had wondered if she would notice my body changes on her own, but that didn't really happen because it was only a month or so. Anyway, this has really sucked because she is now driving the bus to divorce town, if a little more slowly than she would have if I had done HRT without telling her, but at the same time I feel like the whole thing is inevitable because you can only keep your fingers in the dam for 40 or 50 years before you get some cracks and leaks around the edges.
My 2 cents are: do enough NBE to figure out if you really want to pursue it or not; go to a therapist; make a plan with the therapist for coming out to your wife. Don't do what I did and make the plan on your own! Also the fact that you are seeing a therapist at all can be your "warning shot" that something is going to change (although sending good warning shots is basically impossible because no one interprets them correctly).