Not an expert but I can speak of my own experience. I suspect you will see some recomping, loss of body fat and some increase in LBM, but nothing drastic. Personally, I think three shots a week is a hassle. Most recommend twice a week but I just shoot 140mg on Wednesdays and am done with it.
After a few weeks, six in my case, you should get a blood test and have your E2 checked - estrogen. If it is elevated, they should give you an AI to prevent the T from converting to E. You should also have your hematocrit checked and plan on donating blood in the future.
If you want to keep the boys the same size, or you still want to have kids, you should get on Hcg. If it's not an issue, don't bother. Hcg has to be mixed properly, and refrigerated, and it's two or more shots per week on top of the T (you can probably shoot them together, but some will disagree with this). If it's not worth the hassle, don't bother.
I'm sure I missed something but there are others that will weigh in.