I have flown the 400 and NG. Doing exactly what Boeing says in the FCTM and I have never landed hard or long, juat nice consistent plonk at around 1,200 to 1,500 feet every time.
I don't think there are that many variables when landing. The important ones are taken care of like speed for weight and speed additives. The only debateable exception is landing at a high altitude field.