Will Ledger recover the same Ethereum account I created the Meta Mask addresses with or will Ledger create a empty new one, since Ledger live can not see balances?
You will be able to recover your addresses, so long as you use the same seed phrases and derivation paths. Even if Ledger wallet ever ceased to exist. You can still recover the funds using another compatible wallet (Web wallet, hardware, or software) Just make sure you keep your seed phrase very safe and also have some idea about the derivation path Ledger wallet uses (I believe it uses the most common one)yeah, the seed phrase is like the master key, but I guess OP is confused as to why metamask will also prompt to backup seedphrase as well, if OP still have lingering doubt, better ask the technicality of address generation in metamask to the ledger themselves since they are the one who know the working mechanism of metamask and ledger integration.
but according to this statement from ledger article however
source : https://www.ledger.com/academy/security/the-safest-way-to-use-metamask
you should record your metamask seedphrase and backup.