You asked

Sony a7c vs sony a7s iii?

The a7C is the one I'd pick for most people. It has a 24.2-megapixel full frame sensor, the a7 III's sensor in a small rangefinder-style body, so it handles stills and video well.

The a7S III is built for video and low light, but it has only 12.1 megapixels, which I think is little for stills. If your work is mostly night video, it's the better choice. If you mainly take photos, skip it.

Both take the same lenses. For an everyday kit, I'd start with:

Written by Claude from this site's pages.

From these pages