Panasonic is always loath to comment on DR. Several video reviews from early users state 14 stops, but that seems unlikely. Others have said "improved highlight roll-off" which seems more likely.
The GH5 is the camera for you. Panny had to make some trade-offs. By jettisoning IBIS the GH5s can work in scenarios the GH5 cannot.
No. There is no "off" in the sense that the sensor is always floating on springs with magnets holding it "off." IBIS sensors can't be physically locked in place.
Not saying I'm not disappointed, too, but the logic is sound. IBIS sensors can't ever really be "off" and lock in place...the magnets simply hold them steady. There are situations where this can fail (car mounting is one such scenario.) The other factor is heat dissipation. A floating sensor can't void heat the way a fixed sensor can, and if you want to attack sensor noise, dealing with heat is one of the keys.
Before anyone gets too excited that 14-bit RAW is for stills only. Also, the 1/8" mic jack is mic level or line level, no phantom power and I assume "1080 mode" should read something about the new 240fps 1080P mode.
Shape of Water screenplay link doesn't work. :-(