A 12 words BIP39 phrase is 128 bits of entropy. Is this enough? Depends on the algorithm.
In either case, you'd absolutely not want to reuse the phrase. AFAIK BIP-32 does not have security guarantees such that you can't find the seed from a set of private keys.
In either case, you'd absolutely not want to reuse the phrase. AFAIK BIP-32 does not have security guarantees such that you can't find the seed from a set of private keys.