Normally the pole foundations need to be a little deeper than the 4" or so concrete of the barn floor.
When I built pole barns for
Lester buildings the posts had a 3' concrete anchor attached to each post at least 5' underground. The frame of this type of building has to endure wind load and frost movement. The configuration of these steel sided buildings is only limited to your pocket book. I built many with large sliding side doors for equipment access and some of the horse barns can get real fancy. I don't see the need for insulation if you are going to have one side open. Roofs are ventilated and with that much wall open area, insulation of any of it won't do much.
I'd suggest to shop around at some of the bigger builders like Lester, Morton, and Butler to see what they have for plans. I guess you can buy kits from the big-box stores and some independents but I've found that these packages rarely have everything you need to even erect the structure. If you have never built a post and beam building, I'd hire it out, there are just too many "tricks-of-the-trade" to get a good result from a novice.