Questions about Walimex Wt-806

It depends. I don't really know what a bowens lightbox is, I guess it's a softbox. The answer is that in the studio you can probably use them but outside in the slightest wind they might fall over. You can put a stone or weights at the base to make them more stable too. But you should consider C-Stands to put the light above the person for the famous butterfly effect. With these, if you want a light above the person you will have the stand in front of the lens.

If the Rollei ring light has a holder for the standard spigots of all lamp tripods, then yes. It looks like this in the pictures: Rollei Lumen Ring (ring light)

unfortunately now. It's better you buy a separately ballhead, e.g. Novoflex Art. No 249104. He works well and is favourable price