The component outputs are the highest quality outputs that the JVC has. To the best of my knowledge, on the 60p can be output at uncompressed. I just recently met with JVC's lead engineer, and he confirmed this assumption.
As to the drives, any HD signal that ever passes through firewire is compressed. If you use one of the firestore drives with the HVX, the same things happens. So, your 720p 4:4:4 footage on the JVC will be compressed to 4:2:0 after passing through the firewire cable to the Harddrive. This means the best way to get 24p footage out of the JVC is to record to tape, and then take the tape through an HDV deck that is hooked to your computer via an AJA Kona LH card using the component inputs. This will give you 4:2:2 footage.
If you want the highest output possible, you can shoot 60p uncompressed hooking your camera up through the component outputs. The look like RCA outputs, but once you plug all three video cables in (R/G/B) it will passthrough at uncompressed.
I hope this helps,
Justin Talley
323.353.8977
profnoxin@gmail.com
www.justintalley.8m.com