I speak partly from my own experience. How you come out to your wife really depends on how you perceive her reaction based somewhat on her knowledge of ->-bleeped-<-. My wife was and still is quite ignorant on this. She is also very religious, and yes, that can also make a difference. She knew I was seeing a therapist. It was necessary for me to eventually "out" myself to her because in the 90's, my therapist was following the Harry Benjamin Standards of Care. My wife was required to attend the last session, which she did. Afterwards she told me she felt like my therapist and I "ganged up" on her. Anyway, I never proceeded with hrt and rlt which was my next step. After about a month she thought I was "cured". Anyway, I've been on hrt for very nearly seven months. She is unaware, which should give you an idea of our relationship, because I do have some rather obvious growth.
I only knew of one other TS and his wife decided on divorce. Not all wives will be like this. I know there are some out there that are very supportive, or at least become so. However one chooses to come out to their wife, her reaction, I believe, will be pretty much the same whether you spring it on her, let her "find out", or open a discussion that evolves around to the subject. The important thing is in how you make her understand what ->-bleeped-<- is, how it effects you, and how it will effect her. It would also help to involve her in your therapy. Understand, however, that her own perceptions, religious beliefs, etc., will drive her to her response and acceptance or lack thereof. The hard part will be to make her understand and be able to explain to her how this doesn't have to be a negative in your lives. She already has a preconceived idea as to what she expects of you as her husband and a man, and you are about to change all that. Anyone who comes out to their wives/family really needs to be prepared with a little research ahead of time and probably either be in therapy or about to enter into therapy with family support.