Would it be possible to run Path 1 with DSP+Fx and Kill-Dry, but Path 2 without Kill-Dry
Yes. Keep in mind, the H90 no longer has a DSP+FX mode like the H9 because you have spillover automatically. You also get a Tails control that controls what happens when the Preset is bypassed (like DSP+FX).
…and change these around per Program/Preset within a Playlist (so long I keep the Dual Routing for that list, of course)?
Yes. Kill Dry can be set at the Preset or Global level and a preset can defeat the global setting.
what I really need to know is if running Dual Routing one can override the Global Kill-Dry setting per Path as I would be using both at the same time but each Path with a Preset, in a way Parallel/Independent of each other??
Yes, as explained Kill dry can be set at the Preset, Program, or Global level.