Probably But that 24 pin connector is just a couple wires split off from the 20 so in essence it's still drawing power from all the same lines..............but yeah I don't any more than that.
Possibly, but I have a 24pin psu, with an adapter 24 to 20 so its future proof. The 24 pin connector has 24 wires coming from the psu. The extra four are for the pcie slots.