"Dych chi'n hoffi Morgan?"
Translation:Do you like Morgan?
No, it's just plural. (And northerners might be more likely to use dach chi rather than dych chi.)
So you'd use it if you're being polite (e.g. to a stranger that you're not on a first-name basis with), or when talking to several people.
wyt ti is the informal form -- Wyt ti'n hoffi Morgan? is what you might ask your friend.