AccountIdToSalt the account id (e.g. 32 bytes of pubkey) is used as a salt to generate the random id from the vrf.
MaxNewAccountsPerBlock. Seems to be related with the random id. Not sure why we would limit the number of new accounts per block in an other way that extrinsic costs provides if not for random id. I whish we could remove this layer of complexity which makes the migration more difficult to perform as there is more useless code to understand, test, and document. But apparently for @elois this is the opposite:
Same for PendingRandomIdAssignments, PendingNewAccounts, RandomIdAssigned event… What a level of complexity for a feature that does not make consensus, will not be implemented in the main clients, and was added by a guy blaming other for slowing down the migration process.