>>3039479>Is imaging stabilization important for freehand shooting?IS and OSS are rather important if you intend to shoot handheld, especially in dark areas or inside.
>Does APS-C offer a significant advantage over m4/3 in terms of low-light/high-iso performance or could it be compensated for with lower F lenses?Yes, significant advantage. No, it can't really be compensated for with lower F lenses. Plus you'd get super shallow depth of field and worse performance with a lower F lens, which isn't always desirable.
Also, take a look at the a6300 too, it has 4k support, and has been under $1000 lately. Lacks IBIS, but most Sony lenses have OSS at least.
Honestly, of the choices you listed, the a6500 is the best. You can go with some of the smaller FF lenses and upgrade to a FF body in the future too.
Also keep in mind, that if compact size isn't super important, you can adapt and autofocus pretty much any modern lens with the a6500. For that matter, manual focus lenses are fun as hell too.