Can anybody explain what's going on in these clouds?

The right edge on the first pic seems to suggest an arcus front of an outflow boundary. The darker triangular cloud in the the middle of the top pic I would guess might be from localized forcing. Almost looks laminar bell-like. This laminar, non-bumpy look of cumulus, is caused by the forcing of air up in stable air. Which would likely be the case behind the gust front.
Clouds behind a gust front of a rain core can look very mean and scalloped. Like inside a whale's mouth? It's often very cold, well colder, and close to saturation. So you can get fake wall cloud piles and whatnot behind these.
Now if this arcus gust front wraps into something more circular up north or NE, then it may well be the arcus of an RFD flung around the meso.