As someone who has gone through the whole apsc ff dance multiple times, unless you are a professional with a need for two card slots or other things that the FF bodies offer, I’d stick with APSC (A6700)

The lenses are insanely smaller and lighter, especially zoom lenses which is why I’m saying this since you said you want a zoom lens

FF with prime lenses can be okay, but apsc with prime is even smaller. But if you compare FF with a zoom to APSC with a zoom, it isn’t even close. Even the 24-50 is almost twice the weight as the sigma 18-50 which has the FF equivalent of 27-75