Is there a noticeable in accuracy with the SA single shot action?
I think so.
I really prefer to build on single shot actions when I get a choice. They are measurably stiffer and I believe offer better barrel support. Competition wise they are often not allowed to compete with the repeater actions. They are usually thought to have an advantage over the repeaters. I agree.
Structurally a tube with only one ejection port is no longer a tube once another giant hole in the bottom is cut. Then it becomes a couple small flat bars supporting the front receiver ring. Also the bottom action lug is vastly better supported when there is not a feed port cut out of it.
Sorry, I don't know the answer to your other Savage specific questions.