Are Cthuloid mutants for earlier historical eras the same as cthulhu mythos ?
Bit out of scope of the PA board, but in brief yes.
With very few exceptions the Cthulhu ranges are based on the author's 1890s-1920s timeline (or brought forward to modern times) so costumes and fashions all relate to then.
However one of the main tenets of the novels and stories is the "countless aeons" of the elder gods, and hence their followers and assorted cults. They are mentioned explicitly from Ancient Egyptian, Ancient Polynesian, Pre contact American Indian, MesoAmerican and Amazonian tribes so pretty much any historical era could be used.
I think it would be great to see mutated cultists and investigators like you have here but from the 17th century for example. Allowing scenarios like the Salem trials or the Hopkins/Stearne investigations in the UK to change from Gothic Horror Satanist witches to a more sinister Lovecraftian aspect.