Make sure to back up your 3 xpubs as well. In case you lose one of your seeds, if you don't have all the 3 xpubs, you will not be able to recover your keys, even if 2 out of 3 seeds are needed to sign transactions.
To be more accurate, if you lose one of the seed phrases, you will need the master public key associated with the lost seed phrase to recover your wallet. You won't need all three master public keys. Two of them can be derived from the two existing seed phrases.
To recover you wallet and spend fund from that, you will need:
Seed A, Seed B, MPK C
or
Seed B, Seed C, MPK A
or
Seed A, Seed C, MPK B
(MPK = Master public key)
Correct. If OP doesn't want to backup all the xpubs with each cosigner's seed, they could back it up as follows:
1. Seed A, MPK B
2. Seed B, MPK C
3. Seed C, MPK A
Therefore, losing 1 of those packets OP will still be able to recover their wallet. At the same time, if an attacker steals one of the packets, they will not be able to monitor your wallet.