How should product split feature adoption KPIs with the product marketing team?

I'd suggest dont split the KPIs. Here is why

Product Management and Product Marketing are two different ways to accomplish the same outcomes. The difference is one is in product and the other is outside of product but both the experiences are touching the same customer and driving the same north star outcomes. 

But in some cases that may not be possible either because of the org structure or just how your company functions. If that is the case I would suggest to map out both the in product and out of product journeys on a unified customer timeline and then go through identifying KPIs, dependent KPIs and counter metrics. Whether the org structure permits or not, Product Management and Product Marketing is dependent on each other, what one does will impact the other one and vice versa.

It really depends on what type of business it is. For instance, a product feature or product should be so frictionless that it allows users to onboard (adopt) easily once they are in the experience. Product marketing is responsible for bringing users to that experience. So it is almost eyeballs vs. activation. In reality these metrics should be shared, and over time broken up where the tech is meant to solve for the customer's need.

It's worth ensuring you collaborate closely with your PMM to ensure you know who is responsible for what along all touchpoints. In general, top of the funnel channels owned by marketing should be owned by their team (social, paid, blog, email, etc). Everything else should be owned by the product/design/engineering team (with the exception when marketing owns the development of those product ie. lead gen with "no code" tools). The touchpoints where marketing hands customers over to the product experience should have the right metrics tracked to understand A) the quantity and quality of users and B) how they are experiencing the product. Regardless of who owns what, product should be sure they have the full customer experience tracked (because if it's not tracked, product will be on the hook!)