[cavy-cool-crazy]

Welcome, philosopig! I have to say I love your pigs names - very original!

Nipping, chasing, mounting, butt sniffing, mild teeth chattering and nose-offs (high nose contests) are normal dominance behaviours, and as long as your pigs haven't got into ball-of-fur fighting in that 12 hours then they will be fine to leave in the same cage. It is a bit of a risk but if they are getting on OK while they were supervised then there shouldn't be any differences when they are unsupervised.
Staying with them for the first hour while they are in the cage gives you a good idea of whether it is worth leaving them alone, as if anything was going to happen it would have happened sooner rather than later.

Same cage with a divider is better than having completely separate cages as they get to know each other over time and so will have more of a chance of getting on if they have 'met' each other through the grids.