Bios Banks = seperate bios can be stored and loaded from each one.
Dependant on which chip you have, if you screw up you can restore by USB cable, or by recover mode ( dip switch )
Cannot cause any real damage unless you write a bad coded bios to chip, and make sure you use bios meant for your xbox version only. Using 1.6 on non-1.6 boxes coudl cause damage as well as reverse.