don't bother with the uprights. You open the door loosing most of the heat.. The ones with windows are nice for ability to see cooking. BUT The window gets dirty fast AND another weak link for heat retention.
Step up another $100 and buy this pellet grill. It's a set and forget unit like all pellet smokers are. PLUS at SW you get another 5% off for .mil discount It's on sale for $399
http://www.sportsmanswarehouse.com/s...9791/cat130905
or this for $200 more well worth the investment
http://www.sportsmanswarehouse.com/s...7282/cat126115
I personally would not smoke in an attached garage, Or detached unless you didn't have an issue with the smoke smell, for a long time.
We use the larger camp chef year round, outside. It's lined with bricks wrapped in foil along the bottom, with a felt welding blanket over it on real cold & windy days
Buy this one and cut to a 3x3 for good coverage
https://store.cyberweld.com/panfelwelbla.html
Regarding rubbery skin on poultry. The key to getting crisp skin is a mayonnaise rub. The oils in the mayo when cooking really crisp the skin up.