It's a matter of preference, even too much of a milder smoke (like apple) can leave a bad taste in your mouth, and a mild application of hickory can be great.
You will have to use trial and error to find the results you like.
My favorite smoke for a milder cheese is apple, for stronger I use maple.
The length of smoking time can vary on the smoker size, and the size of the cheese blocks. I prefer to smoke my cheese for about 3 hours when using the A-Maze-N Pellet Smoker.
Keep a small block of cheese just for sampling in the smoker, and then in the resting period in the refrigerator.
Keep in mind that tasting in the smoker will render a very strong flavor, and may seem like too much. When wrapped and rested it will yield a milder taste. This is a skill you will have to learn as you cold smoke many different foods.
Humphrey's DownEast Beast W/BBQ Guru