It’s better to keep them separated but should be fine. Just make sure to label properly and you can use coin control to make sure not to mix them.
Discussion
Of course, label the accounts, label the UTXOs and make sure they never touch to taint any UTXOs. But there’s really no way to tell they’re in the same wallet right ?
Make sure to verify for yourself but my understanding is that the only way anyone can know they’re in the same wallet is if they get your xpub. You can see it on sparrow wallet.