I would use T & G.... tongues up.... and not use any sealer.... smoke houses are supposed to breath.. I had a low temp smoker and smoked everything in it and then transferred the meat to the oven in the house to finish like pulled pork, brisket etc... worked very well.... It could also be used for cold smoking bacon, cheese, salami etc.... When doing low temp smoking, over long periods, cure must be used in the meat for food safety....
If you want a smoker/oven type unit (like the insulated electrics MES) that is a different animal and insulation may be needed and an interior surface that you may want to clean...
There are so many smoker designs and applications that could apply here, it is difficult, at best, to know what you want to do.....
Dave