Check out Jeff Phillips instructions and recipe for salmon. It's great hot or cold.. Going to try this same method with some tuna next week.
Skin on or off is usually just a personal preference or because some fish is too fragile without the skin to hold it together. Salmon & tuna are pretty firm & good either way. The freeze 1st is because most recipes call for lower smoker temps. around 165 to 180 and pulling the fish at a 145 internal temp. Since many fish have parasites that take an internal temp. of 160 to kill, long term freezing is an alternative kill method. Check out the following link.
I vacuum seal & freeze all my fish & have gotten the best results defrosting by putting the still sealed bag in a bowl of cold water in the fridge.
I do a fair amount of Salmon which is all vacuum sealed and then frozen. I thaw by placing the package in the fridge for 12-24 hours.
For all filet's which is most traditional, I leave the skin on. Helps prevent the meat from drying out. If though I'm doing my Salmon nuggets or Salmon Jerky, skin needs to come off.