I think he exceeds at doing both at once. One of the things I loved most about The Clockwork Rocket wasn't the exploration of a universe unlike our own - to be honest, most of it went over my head - but the characters dealing with very human issues in a very non-human world.

Dichronauts is very similar; in a universe with a slight tweak to the laws of physics, we spend most of the book exploring the consequences of that tweak, but also the experiences of the characters living in it, some of which are a consequence of their world, and some of which feel like situations we could very easily find on our planet.