As a top bar hive would the frames be foundationless?
All I run is foundationless. As a top bar hive, it would have top-bars sized to fit the Lang width of the box. I have run these hives with top bars, foundationless frames, and a mixture of both. I would recommend sizing it to fit medium frames if you plan on doing top bars with it, as the deep size box is too big for top bars in my opinion. When it gets hot, the comb gets heavy with honey and collapse becomes a worry. With a box sized for mediums, this is less a concern.
With foundationless lang frames, you get all the benefits of both style hives.
I cover the vent holes with a small flap of roofing felt in the Winter to keep breezes from chilling them too much. I have also put the vent holes on the bottom with good success, but put them on the end near the top to let out Summer heat. I also tried screened bottoms, but they were more trouble than they were worth. Better to get bees with survivor genetics.