Regarding getting a good draft, this is a common misconception for pellet grills. The burn pot on pellet grills receives oxygen via a fan unit. As such, there’s no need for a draft to get a measured burn in the traditional sense. Most pellet grills lack sufficient insulation / gaskets, etc to prevent smoke from leaking out of the body. So, unless you’re going with the Memphis or something that uses oven style insulation, you don’t really need a chimney at all IMHO.
If you are looking to produce competition quality barbecue in your own backyard, then look no further than the Pit Boss Deluxe Wood Pellet Grill and Smoker. This grill has the most versatile cooking system ever built. Sauté, Stir fry, Cook breakfast, or Flame broil dinner in just a few minutes. Sears and broil steaks just like your favorite steakhouse. The 820 Series offers two tiers of porcelain-coated grid construction, totaling 820 sq. inches of cooking surface, allowing you to skillfully prepare food with savory natural hardwood flavor. The Fan-forced convection can bake anything that you would normally bake in your oven. A pellet grill is hands-down the best wood-fired pizza oven that is available. Even smoke your holiday turkey!