The flash is very fast. No charger needed, besides eventually the very first flash, depending on the update level of your vehicle. xDelete will flash the most recent software to your xDrive if not there already.
Is this bad for the All-Wheel-Drive?
No. It won't do any harm, to any components of your car. The xDrive system basically is a clutch that can be opened or closed gradually. The fallback position is open. Not using the clutch, means leaving it in this position, where it is perfectly fine. The best example for this is, that this is the normal operation state above ~ 180 km/h (approx. 110 mph) and that even BMW itself made the recent BMW M5 switchable. The operating principle stayed the same, from the early days til today. It also won’t do any harm to your backaxle or driveshafts. Those components are all the same as on the respective RWD version of your BMW.
Can I run a staggered wheel setup, using xDelete?
You can use any staggered setup with “xDrive OFF”.
With all the other setups, the difference in circumference has to be smaller than 1.5 % as stated by BMW and therefore our recommendation, as with more difference you risk damaging your transfer case.
Too big differences could also irritate the DSC, so choose reasonable differences in diameter. BMW suggests not more than 1,5% between axles for xDrive cars, as a reference.
You can choose more than that, but be aware that speedometers typically only account for 3% difference to standard diameters and then start reading wrong, which by itself is forbidden in most countries.