Hot smoking - Basically you want to get the internal temp of your fish up to 71 degrees at the very end to make sure you have killed all the bacteria. I think with fish you can go a degree or two below that, compared to chicken and pork, but 71 is the FDA approved level.
I smoke fish for 3 - 4 hours at about 67c in the bradley then at the end crank it up to 73c (bradley doesn't have 1 degree increments) for 20 mins to an hour to get up to temp. Often I do this without smoke if I think there is a nice smoke colour on the fish. At this stage I often baste it with sugar mixture to get that sweet caramel taste on the outside of the fish.
Key to moist fish is brine, water bowl in the bradley and you do not heat above 71 degrees internal temp... even if it has been in the smoker for 6 - 8 hours. Note with water in the bradley, the fish will take a lot longer to get up to temp. This is called the stall and is caused by water evaporation on the flesh/skin of the fish... esentially the same as sweating. Just ride through it... I've had. A good smoke takes time.
Cold smoke is below 33c. You CAN NOT do this in the bradley without the cold smoking attachment, as just the smoking plate heats your bradley up to 50c in summer. You need to stay below 33c to prevent bacteria growing for a cold smoke. Put a bowl of ice cubes in the bottom, put the bradley in the shade do anything to keep under 33c. Over that and you may as well hot smoke to be safe. Cold smoking key is the brining for something like cold smoked salmon - silky texture subtle smoky taste. For something like kippers more important is smoking them for ages 8 + hours - strong smoke flavour.