I run freight & passenger trains, but I don't mix freight with passenger. With freight trains I try to run hopper cars with hopper cars or gondolas, and I use a caboose with every freight train, as I think it looks better then the end of train device on a freight car. For my passenger trains I run only a matched set of passenger cars as it looks better to me.
I try to keep my motive power correct for the particular version of freight or passenger train I run.
Lee Fritz