Re: cresting- breeds that have been bred with crests for a long time, like silkies, polish, brabanters, Cream Legbars, etc, breed together fine with minimal problems from the crest. Cresting is created by a skull deformity, and I have heard silkies are more prone to death or permanent injury from a head blow due to this, also to wryneck/vit B deficiency although I'm not 100% sure that's linked to the skull deformity. I have not heard either of those things being a problem in the other crested breeds. My Cream Legbars at least do not have these issues.
HOWEVER- one breed that is having trouble with the cresting is Swedish Flower Hens. When Greenfire Farms imported their first flock, they selected from a breeder who did not like the crests and bred for non-crested birds. Then they imported another line that WAS crested- and crossing these two lines DOES seem to be very much a problem if you breed crested to crested. The line that is not used to having crested genes does not handle a double dose of cresting well and you get lower hatch rates and higher chick mortality related to the cresting deformity. For now it is recommended in the US to breed only noncrested to crested, or noncrested to noncrested, but to avoid breeding two crested birds together.
My understanding is that Cinnamon Queens are a type of sexlink. Sexlinks are created two ways- either silver based hen X gold based roo to make red sexlinks like Cinnamon Queens (males are white/silver), or barred hen X nonbarred rooster to make black sexlinks (males are barred). Cinnamon Queens in particular are a "trade secret" in the specific breeds/lines used by the hatchery to create them- they are designed to be laying machines and they are very good at that for 2-3 years.
Phew!!! Crisis averted!
