I only have one but I do know a little about them.
You'll find, as you've already found, that few people raise them and even fewer breed them. But there are a few BYCers that breed them on here. They may become more friendly when socialized with humans. Adults don't take to confinment well and like to free-range. They're pretty good fliers and many like roosting in trees. They're cold hardy.
As far as general information goes, they are being worked on in Silver Spangled, Golden Spangled, and Black. But I think only the Silver Spangled coloring is in the U.S.
If Spitz chickens aren't around people often, they can become a bit more flightly. My chick is roughly 11 weeks old and still doesn't like when I hold her.
There is a standard for them, even though they aren't yet a recognized breed. One of their most important flaws that have to be bred out by breeders in their crest. Hatchery chicks sometimes grow crests like Polish fowl when the crest should be smaller, tighter, and forward pointing. Spangling can sometimes be an issue.
Don't take my total word for it, though. Hopefully others will respond or correct me if I'm wrong.