Migrating old wallets questions

I've got two different nodes (both on version 26) up and running, and each of them is using its own wallet.dat file. The catch is that these wallet.dat files actually have the same keys. So, if I go ahead and migrate the legacy wallet from one of these nodes, will it mess with the other node’s wallet? Like, will the keys from the legacy wallet become invalid or anything?

Migration of a wallet does not invalidate keys. It only changes how things are stored and organized in the wallet. While you will get newly generated keys and all previous keys are "retired", those keys are still in the wallet and can still be used to send and receive Bitcoin. Migration is a local operation that happens on a wallet file. It will not change any other wallet file, even ones that share the same keys. There is no signal nor anything observable that some other wallet on another node would be able to tell that a wallet has been migrated. However, if you have 2 copies of the same wallet, migrating both of them will result in a completely new and different set of keys being generated from that point on. After the migration, they will no longer generate the same addresses, although all previously generated addresses (and their keys) remain, as stated earlier.

thanks for the great answer.