Marshall, Welcome to the SMF.
Its a bit hotter the higher you go. I never worry about which rack the meat is on unless its poultry which for safety reasons should be on the lower rack so it doesnt drip on other types of meats. If your just doing one type of meat any rack will do. If I am doing only one piece of meat I put it in the middle.
Probably the most important thing for smoking is to make sure the temperature is right. I put a thermometer , The type you hang inside your oven, on the rack right beside the meat. Once you get the temps right and have some thin blue smoke caressing the meat your in business. Good luck.