I mentioned the MRD in previous answers, which I think is great at informing individual projects or initiatives. At a higher strategic level, I find that Product Vision docs are valuable at helping PMMs, PMs and other cross-functional partners align on the multi-year vision for the product. Having alignment on where you want to be in the next 3, 5, and 10 years is really important when navigating the day-to-day of customer feedback and product roadmap prioritization.