As far as I know they dont overbook F. I've heard (and never confirmed) that EK overbooks Y up to 20%, which then allows for 10% no shows. You can be sure that they have some complex revenue management algorithms which would be route dependent.

For example, the SIN-MEL-SIN traffic is highly seasonal - so they could use a lot of historical data to manage the load and book each cabin accordingly. Same goes for DXB-LHR - where I dont reckon they'd overbook as much. I think they would only overbook J by 10%

Just my 2 cents...

PS Lufthansa has just started overselling their F cabin on certain routes...