I have tried the whole "clone a track" then nudge one a few clicks one way or the other. For me, that didn't work properly to give the correct results I was looking. Since the tracks are identical to each other the possibility of comb filtering and other problematic issues can arise.
I prefer to record several tracks. Now doing that can take considerable time since if they are both going to be heard as in the pop music example...they have to be dead on ringers with tempo, phrasing, nuances, and pitch. (of course pitch correction and manipulation software can really help in this endeavor)
The Beatles used to use a method like this....and I heard somewhere that they (Paul?) would spend dozens of hours, sometimes many days, just working on the vocal tracks to get it exact.... since I don't think they had access to such tools as melodyne back in the day.