Yes. The price would be much too high for a single China Lamp Tripod from Walimex.
With this set of 3 of the popular walimex WT-806 Lamp Tripod, you are perfectly equipped for many lighting setups: with the help of the tripods, you can, for example, use main light, fill light...
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)
Hi Ferdi, I use the lamp tripods for Godox AD200 with soft-box. The weight is about the same, if not heavier with soft-box. They are quite stable, but I would advise you to put a weight at the bottom of the feet if they are not standing in the corner and you could trip over them. Put a weight at the bottom of the feet. It doesn't have to be something expensive like Walimex Studio Sandbag, a bag with sand will do.
You also need an umbrella tilt. Preferably a sturdy one from Manfrotto. Manfrotto 026 Lite Tite Universal Umbrella Head (Various)
If you buy cheap, you may pay twice.