I will present recent high-resolution measurements of ISM structure, radiation feedback, and PAH fractions in nearby galaxies based on mid-infrared emission and optical spectroscopy from the PHANGS JWST and MUSE surveys. JWST mid-IR images reveal complex substructure that simultaneously traces the distribution of dust and gas as well as heating from young stars. We measure the distribution functions (PDFs) of this mid-IR emission and show a common behavior where star-forming regions form a power-law tail while diffuse emission exhibits a log-normal distribution, which traces the underlying gas column density distribution. Within the star-forming regions, we combine JWST, MUSE, and HST to measure the strength of dynamical feedback mechanisms, including a first-ever estimate of the strength of total IR reprocessed radiation pressure in a large (~18,000) set of HII regions. We find that the IR pressure term is of order 5-10% of the UV radiation pressure from young stars, and that both terms are typically subdominant relative to thermal pressure from photoionization heating. Finally, we will share new results on the contribution of old stars to the gravitational potential of HII regions and molecular clouds, and on the variation in PAH abundance observed by JWST in the diffuse ISM of more than 70 nearby galaxies.