Splitting your seed phrases into two locations is necessary because if a natural disaster like earthquakes, floods etc or an accident like fire happens in one of the locations where you stored your seed phrases, you can be able to recover it in the other location
I am still not sure about what OP is actually insinuating in this thread, splitting the seed phrase into mean in my perception means that 12 words are splitted into two halves (6 words each) been saved differently, if this is what OP means then it is a very bad idea because losing one section can cause one to lose such wallet. But if it is saving the full seed phrase in two different locations then it is a great idea because we never might know what Calamity will be fall one location.
Multisig and preferable to me if two or more people own the wallet or even if it is one person but he has two or more devices to set up the multi sig wallet but if it is one device it reduces the purpose of the wallet as it is still a single point of failure.
You can also add passphrase if it is not a multi sig wallet as a second layer of security to the wallet and both to be safe in different locations