I'd go with having them stand with other Kreons in combined mode personally. They are a little bit more special that way when you compare them to other Kreons.

As for other bots, it depends on the group. If their colours all look similar and they match nicely, then the individuals standing next to each other make a good display. You can really see that they are a team. But then Combined modes are usually impressive.

If I had them on display, I'd alternate. But Kreons, definitely combined.