RE: Good cam for Zagi? (any of these?)
depending on the prop, almost any motor, esc, prop combo is posible. A stock zagi 400 motor 6v speed 400. is a little slow with 2 cells, but will quickly burn out with 3 cells. A better choice would be a 7.2 or 7.5v speed 400 on 3 cells. Your stock esc will usually work, but it lacks a 9v cut off which is needed to prevent dammage to a 3 cell lipoly pack. A 2 cell lipoly will usually be caught by the low voltage cut on most stock esc's. I have flown my stock zagi with a 2 cell lipoly, but it really lacks zip. By the time you buy a new esc, and speed 400 motor, It's probably worth the extra to just step up to brushless. Take a look on another forum to see what everyone is using on a zagi. If you can spin a bigger prop, it will fly longer. You arn't trying to build a speed demon. Try to stick with a 3 cell 2000mah pack for the motor. Anything bigger gets pretty heavy if you add the camera and such. Trying to use your stock nicad pack will usually be too heavy once you add everything else, it has been done, but a light plane flys better and will be more forgiving.
Yes separate batterys for the tx is a good idea, it can be done with the motor battery but can lead to problems.