It's extremely common to have extra noise when you have digital pedals in front of the amp, with the amp set to a high-gain. The H9 is indeed quite noisy in front of an amp. I don't know if the H90 will be different, I hope so.
He's completely right about the AD/DA stages causing extra noise. Whether it breaks your tolerance threshold is another thing.
I use delays and reverbs in front of the amp, never in the loop. That's my style. But I sold my Eventide Timefactor and SPACE for precisely this reason. So yeah you do need to be a bit careful when running those kind of things in front of the amp. In the loop, pretty much anything will work.
I don't personally think analog dry-thru is all that important. If you're running a delay or reverb, the wet portion is still introducing that AD/DA stage, which is the thing that causes noise. So analog dry-thru isn't really saving you all that much in terms of noise. All it is doing is ensuring that you can't get certain sounds via the DSP - 100% wet reversed delays and things like that.