Thanks. So, the xpubs will point to the right addresses with or without the derivation paths?
Not necessarily, no. It depends where you get the xpubs from.
If you are using the xpub already at m/49'/0'/4', then it will derive the right addresses. If you are using the xpub at m, then you will need to specify the derivation path.
What is the difference between m/49' and m/49? So far as I can see, the derivation paths for all my multisig wallets are hardened (i.e., m/49).
m/49 is unhardened. m/49' is hardened. The relevance is that unhardened levels can be derived only using public keys, while hardened levels require the private keys. In short, they are entirely different numbers and will derive entirely different addresses.