Mazda3 = Cruze sizewise. Mazda2 (not sold in US except as small Toyota/ex-Scion) = Sonic.
Front seats are all the way back in the Mazda3 photos. That limits the back seat size greatly. Yes, the C pillar is a big metal slab blocking light and views, but GMI is the place where the alternative fixed third window gets trashed too
The back seat of the Toyota C-HR is actually much worse for the upswept rear window blocking light and life