What's the ideal working relationship between PMM <> PM?

Ideally there is mutual respect, trust, and appreciation for each role. I think about great sports teams - the roles of defense and offensive players. The attributes of what makes great teams thrive. It is camaraderie and alignment on the greater why and outcomes. Doing whatever it takes - even if that means passionate debating. Supporting one another for the Customer. For the Business.

We don't have to be "bff" with product for things to work. We need to act as counsel and a solid teammate so the product org is backed by reason and not biases.

The worst product <> product marketing relationships are when product uses PMM as a scapegoat for their failures. Each remit has to take radical ownership of their remit and perpetuate trust and mutual understanding. If trust is broken - the process is doomed to fail and CX will suffer.