I have often heard the fastest point of sail is 120 degrees from sailors. All of my reading has indicated that 90 degrees apparent to the boat would be the fastest. This would make sense being 120 degrees true wind would be about 90 degrees apparent, depending on forward speed.
The reason for my questioning is, I can sail fastest with apparent wind 90 degrees up to 45, but once I fall off and get the wind at anything aft of 90 the boat slows down.
I have often read about sailors "screaming downwind", but have never even come remotely close.