Do they have an eSIM ?

See -> Check your Apple ID device list to see where you're signed in

Check your Apple ID device list to see where you're signed in - Apple Support

• You can see devices that belong to you.

do the parenthesis mean esims?

It's how they added the iPhone type to the iPhone name.

Go to -> General -> Info -> Name.

The name of a phone in Settings, general, about is often "iphone". If the account has had several then the name would have been incremented with parentheses to distinguish between them. I prefer to rename mine "LD150's iphone12" etc to avoid this

If they only have one iphone (the iphone 11) then the iphone(6) is historical iphone the latest in a long list of iphones, and can be deleted. If they have another iphone then it is probably that one and should not be deleted but could be renamed.