I have 1 Rouen hen and 2 Muscovy hens and they get along great! They have somewhat different body language and different voices, but they understand each other without issues. My Rouen is a far more regular layer as she lays steadily, while my Muscovies lay a clutch and then stop for a bit.
Muscovies can get intensely broody, which is good if you want ducklings, but can be challenging if you either don’t want ducklings or don’t have a drake.
One of my Muscovy hens sat on an empty nest for two months, desperately hoping that ducklings would magically apppear under her.
Nevertheless, I highly recommend Muscovies (and Rouens too, for that matter).