RE: Should I get a 50-60# or 60-70#
Go with what you can comfortably shoot.My bow at 703# feels easier to draw than my old Whitetail Legend does at 60#'s. If you can shoot 70#' sitting down or at odd angles go with that. You might not be able to do it at first and it may take time. If you have to jank all over the place go with 60#'s.
Yes, the new 60's shoot like the old 70's. But why not go with the highest DW you can? Your performance with even heavier arrows will be better than that same arrow from a 60# bow.