You asked
Sony a6400 vs sony a6700?
The a6700 is the one I'd pick if you can stretch to it. It has stabilisation built into the body, subject-detection autofocus and a proper grip. The a6400 is smaller and still very quick to focus, but it has no in-body stabilisation, so you'll need stabilised lenses for slow shutter speeds.
Both take the same lenses, so the choice comes down to the body. On the a6400, I'd pair it with the Sony E 18-135mm f/3.5-5.6 OSS for an everyday travel kit. On either body, the Sony FE 24-105mm f/4 G OSS is a versatile standard zoom.
If you want the lightest setup, Sony a6400 specs and lenses and Sony a6700 specs and lenses list everything that fits each body.
Written by Claude from this site's pages.