“One other question, where exactly is “homo sapiens neanderthalus” extant?”
Right here - all around you. Ever met a redhead?
My understanding, which is admittedly limited, is that the genes that cause red-headedness in modern man, and those that caused it in neaderthal, are two differnet gene complexes.
Still, assuming they’re not, modern red-heads can freely interbreed, with fertile offspring, with non-redheads. Which pretty much definitely says they are all the same species. God bless redheads.