The problem is that sensors hate it if light hits them in all too angled a fashion, so short focal length lenses that are simply very close to the sensor and project light in a "wide funnel" fashion can create surprises (eg color vignettes or very bad corner performance).
The most radical option is using an 28mm or 35mm rangefinder or enlarger lens of true ...
From a still photographers perspective, you can roughly describe, in the APS-C series:
a6100 as an a6000 Mk. II, a6000 as a NEX-6 Mk. II
Common: Slightly less sturdy construction, no IBIS, no good support for adapted AF lenses (PDAF)
a6400 as an a6300 Mk. II, a6300 as a NEX-7 Mk. II
Common: Sturdier chassis, good support for adapted AF lenses (PDAF. Does ...