As long as you bought your ledger from an official source, the seed is all you need.

The seed should already be pretty random and you will definitely be able to restore your coins as long as you write down the right seed as the seed nmemonic is just a large number moved into words and there are so many copies of the algorithms for the derivation paths it'd take every computer to be destroyed and every printout of the code for the mnemonics to be irrecoverable (which would've wiped out bitcoin too).