The bootroms are exactly the same for all 3DS units and include no unique data. (You can probably find them for download if you look hard enough – but they're kind of uncommon since they're not legal to distribute and so easy to dump.)
Yes. Backing up the full sysnand from one console and writing it back to a different console is a surefire way to brick a system. (The CTRNAND is a different matter.)
The OTP is also unique and I think is stored separately from the NAND, but it has been a very long time since anyone needed to dump the OTP.
thanks for this advice, very helpful.
i just started using fastboot and found the script to dump both of the bootroms, the OTP and the seed.
i thin im all set. thank you again!