Swimming will feel great! It was the first normal athletic activity I was able to do (sort of do).
Flutter kick will be good for your lower abs. Pulling will help strengthen your arms and upper body and the whole shebang will give you an aerobic work out. I remember struggling with the kick at first; my legs felt not completely in my control. It got easier each time.
Breaststroke took a while to put together. A basic, not technical frog kick was good for strengthening ab and adductors. I could not do it at first, too weak. Then as I got stronger and worked towards a correct kick, the various pieces slowly (slowly) fell into place, like the pointing and flexing of the feet and the whipping of the lower legs.
Backstroke was finally pain free. The roll used to hurt. It may hurt immediately post op. Fly? Well, that took me a while, too. Weak abs and general stiffness. I couldn't snap my legs for months.
It is interesting there is disagreement about breaststroke kick. Maybe it stems from how weak we are at first?
I did have to be cautious about diving, flip turns, and pushing hard off the wall for six months. Some parts of those movements violate the post op rules, or can. The other caution I'll offer is on open turns if you always push off the same way, on the same side, you will feel it. I felt excessively stretched on one side after swimming long periods and learned to alternate sides.
Keep walking in the pool and doing those stretches. Walking sideways really helped me get my ab and adductor strength back. Pat has some water exercises on this site.