OCS4, insulation is a consideration, but it is up to you.
I think that what people are saying is that due to the thin walls of the barrels any sort of wind, rain, etc. COULD drastically affect your cooking.
Firebrick would be a great heat sink, and can help to moderate, but add weight quickly. Wool insulation is pricey.
I've done chili cook offs and cooks that were in wind, rain, etc. and they are terribly frustrating.
The welding blankets can be added on, or taken off when conditions are beautiful.
I use tarps and tarp clips as wind breaks and those work fine. I have even driven rebar into the ground put PVC pipe on as vertical supports and then placed black trash bags ove them to act as a fence.
Consider what is best for YOU, and go for it! You'll be fine, keep up the good work!