I liken the 89 neck to a Wizard III. Others may disagree. Also note that Variaxes tend to weigh more than their counterparts with less hardware under the hood.
1. Everything transmits over VDI. Unofficially, you may use any generic CAT5 cable of desired length. Officially, use only official cables.
2, 3. The factory firmware tunings on the 89 are silkscreened on the tuning knob, but may be programmed to be whatever you like.
4. Don’t know why you’d want to replace the physical knob, but it would just be a matter of finding the part.
5. It’s a floating Floyd Rose with pull-up routing; range determined by your setup.
6. All JTVs are powered via either an onboard lithium-ion battery or via VDI. Powering via 1/4” requires a proprietary breakout box.
7. As I recall, Plugging 1/4” and VDI simultaneously is actually required when using the Workbench software independent of a POD/Helix USB interface (the 1/4” jack turns the guitar “on” and allows for real-time monitoring of tweaks)
8. Yes. You may program your Helix/POD patches to have the physical Variax controls slave to preset values In the unit.