Butyl tape / sealant / or both?

As long as the caulking stays flexible (is highly rubberized), it will be fine, but butyl (aka tremco tape) is often much easier and less messy to work with, and does a great job of sealing. We use it for joining commercial/industrial duct work, and I used it all over my bus conversion... joining sheet metal panels, installing windows, bag awning rail, etc., and it can be applied in the cold, whereas most caulkings cannot.