You have a floating dip tube so no need to dump trub. Would be useful to do that if you wanted to serve from the fermenter or use it as a brite tank too but if you're pulling the beer off to package in a keg or bottle from then no need to dump trub.
I have the older version with the screw up jar with is a nice idea but not executed well. Often the amount of trub is just slightly more than the volume of the jar so you can dump one jars worth of trub then have say a quarter of a jar remaining in the fermenter and you're not going to want to waste 3/4 of a litre of beer to dump the remainder of the trub, so better to just leave it.
I never had any great success with dry hopping via the jar...the pellets were never fully evacuated from the jar once you opened the valve and you got a good chunk of them that just sat in the jar and never mixed with the beer. Personally I just dry hop in a keg and get far better result, though the hop bong looks good. If I had the later version of the fermzilla with the triclamp fitting I'd ditch the jar altogether and go for a more conventional valve setup as you have with most other Unitanks.