What can 1 master public key in a multisig reveal? Assume you have the following situation:
You are going to create a new multisig wallet with Electrum.
2 signatures are from old hardware wallets and 1 signature is brand new. 

The new multisig will only be used with Electrum and Electrum personal server connected to Bitcoin Core. The 2 old signatures from the hardware wallets has been used with the hardware wallets own wallets (like Ledger Live and Trezor Wallet). Then I guess we can assume that the master public keys from those 2 wallets has been uploaded to some server somewhere and could be "leaked".

From a privacy standpoint, if I create a new multisig, is it possible to get any information from the 2 old master public keys? Or, do you need all 3 keys?

Would it be a good practice to create two new master public keys (by "reinstalling" the old hardware wallets) and create a new multisig with 3 brand new keys (and treat them with more care in the future)? Or is it fine, because 1 key is new?
From a security perspective related to spending bitcoins, since only the master public keys have been compromised, there is no way that the attackers can derive the child public keys as they do not have access to the chain code. However, if the chain code is also revealed, there is no way to derive child private keys and hence the attacker cannot spend the funds. So if you are trying to create transactions with 1-of-3 or 2-of-3 multi-sig, the attacker still does not have access to the signatures (since he does not have the private keys)

However, if you are going to create a P2SH address of all the 3 public keys involved, there is no way anyone can recreate this address even if they know the 2 of the 3 public keys.