My go-to Magnum handgun powder is Accurate #9. It can be downloaded slightly, and has a lot less muzzle flash than 296/H110.
There is good info on the Accurate site.
A hot primer is not a bad idea in the 357. I prefer the Fed 200, which is a small rifle primer used in 22 Hornet, 30 Carbine, and 357 Magnum factory loads.
DO NOT USE THIS PRIMER IN HIGH PRESSURE ROUNDS, OR IN THE AR PLATFORM. They will pierce in one case, and exhibit slamfires in the other.