It's a while I'm thinking about it, but I didn't reach any conclusion about my tastes, so let's hear what you think.
Elk inherits SMF way of "watching" a topic (that is reply and then see it in the list of unread replies). Then there is the "notify" button that sends you an email.
Other software have just the "watch" button, that populates a list of topics you want to follow and gives you the "watched topics" list sorted by latest reply.
As I said, I don't know which method I prefer. I like both of them because if I want to know what's going on in a topic, I most likely post a message there (just because if I'm interested I have something to say), but from time to time it may be handy to know what's going on in topics I didn't post in.
That said, I don't use regularly the unread replies function, because I use it as a sort of "bookmark" to remember things I have to do/answer, so I'm really not the best person to answer this question. lol
Better avoid emails and use a watched topic highlighting of some kind on " New Posts ".
I prefer the Watch feature. I seldom use the Notify ( though I have it enabled here ) for the reason that the amount of email that can be generated is astounding.