Norm, many thanks for the welcome back and all the info. It reads like Prepar3D v5 might be much more pain than I anticipated. I only have FS2020 standard edition via a Microsoft Game Pass subscription, so not like I'm heavily invested in it. I did reinstall it yesterday and noticed that it performs more satisfactorily since I last tried it. I don't know if that's due to my PC upgrade or updates to FS2020 - probably a bit of both.
I downloaded all of the RTMM scenery so that I can give FS2020 a better try out for bush piloting. I am very happy to see a PC-6 Porter seaplane, as although I've never owned one for FSX-SE, I considered buying the MilViz - very nice ride. My biggest issue with the sim is the HOTAS configuration. I though I encountered a poor control UI in IL-2 Cliffs of Dover, but IMO the FS2020 UI is even more cringe worthy. I find it annoying that in order not to have my Xbox hand controller auto-configured, I need to either unplug it before staring up the app, or go through and delete every assignment.
I also find the sensitivities for control axis to be off, whereas the sensitivities for both my throttle quadrant and rudder pedal are good right out of the box for Xplane 11 and for FSX-SE + FSUIPCv4. I do remember them being even worse the last time I tried FS2020, so I guess there's been some effort to improve. Biggest struggle for me is to get my slider throttle on my stick working for elevator trim. While it works just fine in XP-11 and FSX-SE+FSUPIC, it's hyper-sensitive in MSFS. Meanwhile the sensitivity tweaking is much more finnicky and archaic that one I've experienced in XP-11 or FSUIPC.
Other big issue for me is hydrography and water effects - woah do they seem to be lacking. There not XP-11 bad, but much below what I even have in FSX-SE with the Accu-feel addon. Every water surface is like a glass lake - almost like those old museum dioramas where inches of lacquer were poured in for water. Maybe I'm missing something though, but I looked through all the general config menu, but couldn't find anything for better water effects?
I did try running in DX12 beta for graphic settings, but I didn't notice any visual changes - just much choppier frame rates?