I say the Hazelhatch option would be best. Very quick into Heuston then if you get a mainline train. Not sure about the commuter trains as they will stop along the way. There is parking at Hazelhatch but I have no idea how much. Maybe try both options and see which works best for you?
Option 4: The 66X will be the fastest. 30 mins from bus stop to bus stop even with the M50 interchange roadworks. Motorway bus lanes all the way to Hueston.