I usually quote specific messages before I comment on them, but I'm in a bit of a rush at the moment.
Regarding the JH16 Pro being the new king of IEMs: I don't think that's accurate. I think for those given the opportunity to hear demo units of both prior to ordering, it wouldn't surprise me if those orders were split down the middle. Some people like more neutral, some people like more bassy. The JH13 Pro is a bit more than neutral in the bass (and generally neutral through the rest). And the JH16 Pro is even more above neutral in the bass than the JH13 Pro, and similar (generally neutral) through the rest. Again, I could be wrong, but I think as more impressions shake out from others, and as some people get to hear demo units of both, there will likely be a relatively even split on orders between these two models over the long run (again, of course, I could be wrong, and only time will tell).
Regarding the UE18 Pro versus the JH16 Pro: UE18 Pro sounds bloomier through the mids than either the JH13 or JH16. The JH16 Pro has a bigger bass bump than the UE18 Pro I've got. Both the JH13 and JH16 are more neutral overall above 100 Hz. Both the JH13 and JH16 have shimmerier treble at the higher end of whatever my ears' limits are. The UE18, overall, tends towards the sweeter, somewhat more mid-forward, presentation than either the JH13 or JH16. Both the JH16 and JH13 have a more revealing, more reference-type sound. The UE18 Pro is really its own flavor, and the JH16 and JH13 are different flavors of the same reference-type presentation.
Regarding the JH11 Pro: I haven't heard that one, so I apologize I can't comment on that one specifically.
Regarding balanced operation, the Shadow and the Predator: I haven't used any of my IEMs balanced out of the Protector yet (I still haven't ordered my cables). I haven't used the JH16 Pro with the Shadow or the Predator yet.
Regarding people happy they chose the JH13 Pro or the JH16 Pro (take your pick): Not surprising (either way). I feel fortunate to have both now, but I could gladly live with either (if, say, I had to hypothetically send one of them away forever).
Regarding how much more over neutral in the bass than the HD800 the JH16 Pro is (if you're willing to accept that the HD800 is generally quite neutral through the bass, which I am): Without measuring it, I'd really rather not guess at numbers, but I think it's safe to say the JH16 Pro is at least a handful of decibels higher than the HD800 centered at 50Hz.