You cannot leave a V6 in 4HI all the time on dry pavement, there will be ill effects.
There are no ill effects. The 4th gen V6 has the same center differential, so nothing will be damaged if you use it on dry pavement. The parts are basically identical to the V8, but there is a 2WD mode in the transfer case and an Automatic Differential Disconnect (ADD) up front. Just don't lock the center differential on dry pavement. The 5th gen (except Limited trim) has no center differential, so it would be bad to leave that in 4WD all the time.