I'm looking at the GDS file of the example analog project and I see that the substract contacts are nvpsubdiff. I was wondering what the difference betwee this layer and normal psubdiff is. I've just been using psubdiff for my own contacts in my layout. Thanks in advance for the clarification.

Try the complete DRC check. If you're using high Vt transistors with normal psubstrate contacts, normal DRC checks won't be a problem. With full DRC, the distances between the shapes may be enough to trigger a DRC error.

I see. Normal contacts cleared DRC for us.

The GDS file is what counts in the end. The common psub will turn into hv after GDS conversion, if I'm not wrong.