In practice I use the T/D and mid RVRs for a CAT 1 i.e. they both need to be above 550m, dunno what the "official answer" is.
As for not be able to do an autoland on a Cat 1 approach, that is balderdash, you can do an autoland to an approved runway if it is clear skies if you like, in fact it's often necessary for recency (crew and aircraft).