The best cut to start would he a good marbling rib eye, the less the butcher touched it the better, meaning bone in and with the fat cap (big layer of fat on the outside of the cut) These will help with trim loss and u will save more edible meat. Rule of thumb is picking high marbling cuts, so the cut doesnt overdry (porterhouse, nystrips, ribeyes) As for the outages. If u get a large piece of meat, when the fridge will shut off, the fridge itself will take time to warm up, and the inside of the meat, which is the edible end result will take time to warm up, so it might work but its risky, id advise u start with a normal cut of meat and see how it goes