For fastest production, pour at the lowest temperature that will produce perfect bullets. If you pour at high temp, the mold will stay hottest at the lowest casting rate. - No matter how hot the lead is when it runs into the mold, it hardens at the same temperature. The only serious concern with alloy temperature is when using Lee pots in a breezy cool area, which causes the thermostate to false cycle, resulting in alloy temperatures of 1000 deg +, which causes serious gassing off of harmful metals. The lower the temperature you can use, the less your alloy will oxidize in the pot, and the less you'll have to flux.
Sizing heat treated bullets causes a thin surface work softening where the metal is crushed and moved by sizing. It has no effect on performance, leading, or pressure in the gun, nor terminal performance. So this is one of those bits of knowledge we are just as well not understanding if it causes worry.
