Welcome to MF[D], Paul.
I have the same type of Kodak back but on a Mamiya AFD platform. So I cannot answer concerning which H lenses are better in quality, but I can say something about which focal lengths I like to use for the particular "crop factor" of our backs.
Also, I'm taking a lot landscape pictures ... is HC35 the lens to have for this purpose?
Yes, the 35mm focal length is good as it has the same diagonal field of view on the 645H as a 'classic 28mm wideangle' on 35mm format.
My lens lineup is currently a mix of AF and manual lenses: 35/3.5, 55/2.8, 80/1.9, 110/2.8, 55-110/4.5 zoom, 200/2.8 APO, 2x TC from Mamiya; and 30/3.5 fisheye, 300/4 Sonnar from P6/Kiev mount.
Of these, my "normal" walkabout kit is 4 items: the 35, 55-110 zoom, 200, and 2x. This covers more than a 10x range from 35mm to 400mm. I shot all of this range during an 80-minute beach walk the other evening, and never noticed the weight.
Indoors, I usually replace the zoom with the 80/1.9 as my "people" lens. Much faster, focuses closer, great bokeh. The 100/2.2 H lens sounds like the equivalent one you'll want. You ask about the 120 H lens - I would say yes, it is a more typical focal length for portraits than the 150mm, given the crop factor. My 110mm (whether prime or zoom) seems plenty long for this purpose.
Astrophotography: mainly 30/3.5 fisheye, 80/1.9, 200/2.8. Sometimes the other fast primes (35/3.5, 55/2.8, 110/2.8, 300/4) as well. The fast apertures of the Mamiya lenses are critical here.
Ray