Maybe this was already answered in some supplement that I don't have or another, but what happens when a metavariant (as in the Companion) is infected with HMHVV? For example, does an Ogre become a Wendigo, or something else totally?

IIRC, each metavariant simply becomes the same as their base metahuman type. I don't have my SRC with me at the moment, but that is where the info is I believe.

That is the correct canon way of doing things.

Personally, I prefer varying the base version of the vampire depending on the metavariant. It doesn't have to be much - appearance alone might throw the players, but also altered powers based on the differences between the variant and the 'base' meta.

For an Ogre based Wendigo: Why not remove the fur? Ogres are mainly hairless, so make the Wendigo mostly hairless. Ogres lack natural lowlight vision, so maybe change the Wendigo's innate vision to thermographic instead?

A Night One Banshee: Keep the appearance; hair and all. Increase severity of their allergy to sunlight one step (to reflect the NightOne nature). If you want a more powerful banshee, add an extra die to initiative, or Enhanced Physical Attributes(Quickness, 2x/day, ED6 turns) and reduce Intelligence by 1 point (to reflect an inability to rise above it's faster natural responses).