Circumstellar debris disks are signposts for the existence of extrasolar planetary systems and probe their dynamical histories and architectures when imaged at high spatial resolution. Here I will review several recently completed and ongoing projects. First, I will summarize key results from a four-year debris disk survey of 100+ stars in NIR, polarized scattered light with the Gemini Planet Imager. The survey probes young planetary systems (10—100 Myr) for micron-sized dust on Solar System-like scales with polarimetry and high angular resolution. Among the 26 disks detected, seven are scattered-light discoveries, over a dozen are seen in polarized intensity for the first time, and all are resolved on spatial scales of 0.5—7.0 AU (Esposito et al. 2020). Second, I will review three follow-up studies based on one of these discoveries, the highly asymmetric circumbinary disk surrounding HD 106906. Using Gaia and ground-based data, we identify close stellar flybys that externally perturbed this disk as well as others in the Sco-Cen OB Association (De Rosa & Kalas 2019; Ma, De Rosa & Kalas 2020). A major breakthrough is that we also achieved the first detection of orbital motion for its wide-separation (737 AU) giant planet HD 106906b using HST data (Nguyen, De Rosa & Kalas 2020). We show that periastron is detached from the planetary region, demonstrating that a Planet Nine-like dynamical architecture can be established early in the evolution of a planetary system. Finally, I will discuss the latest work on Fomalhaut b, the enigmatic extrasolar planet candidate that could signify the direct detection of an extrasolar dwarf planet or the existence of colliding moons around a giant planet.