AGN can have a profound impact on the interstellar medium (ISM), but distinguishing its effects from star formation feedback remains difficult due to the complexity of observational tracers. Using new observations from SWAN (Surveying Whirlpool at Arcseconds with NOEMA), we investigate the interplay between AGN activity and star formation feedback in the ISM on the scale of molecular clouds in M51. SWAN maps multiple dense gas tracers - including HCN, HCO+, HNC, and N2H+ - across the central 5kpcx7kpc of M51 at 125pc scale. This resolution is crucial, as star formation unfolds on molecular cloud scales. M51 hosts an AGN as well, whose molecular and ionized gas outflows are limited to the central 500pc. Thus, SWAN probes the boundary between AGN and star formation feedback in the ISM. We combine this dataset with VENGA (VIRUS-P Exploration of Nearby Galaxies), an optical integral field spectroscopy survey that observes the ionized gas emission lines necessary to discern AGN ionization from star formation. We use well-established diagnostics of emission line ratios to identify where the AGN or star formation dominate the ionized gas. Correlations between dense gas tracers HCN, HNC, and N2H+ are shifted in the AGN region, which itself is smaller than the region impacted by the molecular outflow. Only HCO+ exhibits unexpected offsets beyond the optical AGN signatures, with stellar feedback playing a key role in the relative HCO+ abundance. We also explore whether apparent AGN activity could be shocks, using both velocity information from the ionized gas and molecular shock tracers like HNCO. Both are most apparent near the AGN, blurring the distinction between AGN heating of dense gas tracers and chemical reactions triggered by shocks. A multi-wavelength approach reveals how dense gas tracers reflect ISM changes driven by AGN and star formation feedback, offering new insight into the complex relationship between feedback processes and the physical conditions of the ISM.
