either flap 30 or 40 is ok, depending on field length and what you feel like doing.
the main reasons for using 30 instead of 40 are better approach climb gradient ie higher landing weight and/or lower minima and also better control in strong x-wind landings.
flap 40 is normal for autolands because of better slant vis in low vis conditions but there is no reason why 30 can't be used except for the above.
it's up to the individual.
in the 300's you mainly used 30 in hot weather because of approach climb limitations but apart from icing conditions it doesn't make much diff in a 700.