The company encourages flaps 30 landings to safe fuel. However with any tailwind component flaps 40 is mandatory. Autoland can be done in either flaps 30 or 40, however flaps 40 is recommended except for OEI approaches where it is prohibited for performance reasons (go-around climb). Personally i rather use flaps 40 on the 800 and mostly 30 on the 700. But it depends on the runway, desired turn off and weight and therefore Vref, don't like Vrefs much about 145kts. The 700 is much slower which i prefer, except in bumpy conditions.