Yes. I do salt pepper garlic and a rosemary sprig in the bag. Sear in butter or tallow on cast iron just before serving. It doesn’t need to rest.

yes sear after in a very hot cast iron to build a crust, but do not burn it.

Yes. Make sure you pat the meat with some paper towels to dry it off a bit before the sear. I like to use my cast iron on the stove top when it's cold outside and I don't want to mess with the grill.