RE: backstraps vs. tenderloin
I prefer to remove the tenderloins when I' m field dressing the deer. In any case, they must be removed as quickly as possible since, unlike the rest of the meat, they are exposed to the air and will dry out quickly. If you carry a couple of zip lock bags in your field kit, you can use one for the tenderloins, the other for liver, heart, and whatever other innards you choose to keep.
The tenderloins require no marinade or tenderizing. We invariably grill them the evening of the kill. Regardless of how you cook them, they should definitely lean towards rare. Also keep in mind that venison appears more red for its doneness than does beef. If you cook it until it is pink, for example, it is done to medium, not medium rare, and will begin to toughen and dry out. The same philosophy holds for the backstraps, which I also prefer to leave whole and grill.