I will have to do some research on the different flavors, but as to when to use the oak, I do have some comments.
I add 20-25 oak beans during bulk aging. They are usually used up in 30 days, so if you want more oak flavor, you can just add more beans every 30 days until you get the level of oakiness that you want.
So far, I have had the best success with the heavy toast. I have been able to add a little extra oak flavor, but the real benefit seems to be in the added body. It must be the tannins in the oak.