Specifically on Goin' On, that vocal hook sounds so similar to the vocal snippet that plays before the string outro on the Smile Sessions version of Heroes and Villains. Is there any proven influence, or is it just a coincidence as far as we can tell?
Probably coincidental. Brian and the band are known for reusing various motifs and bits throughout their music in other songs. Take the similarities between BW's "Walkin' The Line" and Al Jardine's "Looking Down the Coast" for example. Hell, their early previously unreleased song "All Dressed Up For School" morphed into "I Just Got My Pay" before finally achieving it's Super Saiyan form of "Marcella".
And yeah there seems to be more of a direct Queen influence going on here.