Resting meat, real or myth

Yes, measurably: resting lets the temperature even out and the juices redistribute, so less liquid runs out on the board. Five minutes for a steak, twenty for a roast, and loosely covered rather than wrapped, which steams the crust away.

Heat and order. Take the pan off the heat before the butter goes in, add it cold and in pieces, and swirl rather than stir. A broken sauce is usually rescued by a spoonful of cold water off the heat, whisked hard.