I'm generally a fan fan. helps ensure more even heat, though can be a bit drying and it can reduce the cooking time so, especially with American recipes, be sure to check things a bit earlier than you might otherwise. As for the top/bottom, depends on what your oven is like. If the top is just the exposed grill element, don't...

For puff pastry especially, you want high heat and good circulation because it is entirely steam leavened. You want the moisture in the pastry to turn to steam very quickly. I love the convection setting for general baking, but not for custards. Convection heat tends to form too much of a "skin" on custards.