Stopping T before surgery is currently debated by the genderteam here in the Netherlands. So far, they have always required you to stop 1-2 weeks before the surgery, and start again 1-2 weeks after. It was said having T in your system makes the healing slower and increases the risk for infections. I have never seen research that backs this claim up, and I think the doctors are seeing that too. Right now some say you have to stop, while others do not. For my own surgery, which was a cooperation between two hospitals, one doctor told me it wasn't needed to stop. About 5 days before my surgery the other hospital called and told me to stop. So yeah...Widely debated. In the end I stopped for 1-2 weeks and didn't notice a single change.
In any case. If you stop for 3-4 weeks you should not see many changes. Remember, it took way longer for that to see changes when you started. You may think your voice gets higher and your fat is shifting back to female areas, but that is mostly dysphoria.