First - let's skip past advice relating to the fact that it's still a new update and it's often best to wait. Well aware of that. :) 
 
My build is mostly EVGA - SR-3, Nu Audio Pro, 2080ti hydro copper, psu, etc. I'm running into several stability issues that I'm not seeing referenced in other 2004 discussions and given I'm mostly EVGA wanted to share here and see if others had run into it. 
 
Issues Observed:

• (This is the primary issue of concern for me as it's the only one that I simply have no idea at this time on underlying root cause unless it's something as simple as Nvidia driver) While running a game in windowed mode, after a period of time, all other apps will go non-responsive. They will go 'not responding' for X amount of time. Once they start working again, it's often for only seconds before continuing to be non-responsive. This seems to occur in basically all apps except the game itself  (e.g., browsers, MMC, Discord). Force closing apps and restarting them has no effect. Closing the game has no effect. Only fix is to fully restart. However the Windows restarting screen often gets stuck here with the spinning wheel so I typically have to hard power down at this screen.
• Audio is so distorted in Nvidia Shadowplay / Highlights that one cannot hear a thing (game audio, not mic audio). This one actually started a couple weeks after going to 2004 so could be in relation to 2004 + a recent Nvidia driver update. My Nu Audio sample rate is typically set to 32 bit / 192k. I tried going down to 32/96k and no difference. Obs is able to record footage including game audio just fine so I *assume* it's probably an Nvidia driver issue. 
• I WAS getting routine BSOD for "machine check exception" which consistently occurred while playing a full screen game and minimizing to do x, y, z. This has sense stopped and I think it was due to my prior power config. I had Nvidia Control Panel's power mgmt setting at the global level set to Adaptive and then for my primary games set to high performance. So I'm guessing this caused a power mgmt conflict that resulted in a different (and insufficient power draw) while an app set to high performance was minimized. 

 
Things I've tried:

• Reinstalled or updated virtually all hardware drivers possible (including Nu Audio). Though I noticed there haven't been any SR-3 driver updates posted since Jan and no Nu Audio Pro updates since March. 
• Tried clean reinstall of Nvidia's latest driver. Upon seeing no change, did a DDU and reinstall. 
• Removed most unneeded software to reduce chance of conflicts. 
• Disabled exclusive mode on sound devices. 
• Haven't found anything of value in the Event Logs. Not seeing any errors of note/value. 
• Checked device & driver status in device mgr. Disabled only extra audio device which was my monitor listed due to the nvidia displayport connection. My mobo's onboard audio is disabled in BIOS. 
• Re-ran 3DMark, memtest pro, and other stress testing solutions to validate my hardware is still stable. 
• Ran chkdsk + sfc just to confirm no drive or OS file corruption. 
• Reduced startup items and running services to a minimal set. 
• Reviewed the crash dumps from the BSOD in the earlier causes but non-relevant given BSOD issues resolved since the power mgmt change. 
• Once setting Nvidia Control Panel power mgmt setting globally to high performance, the BSOD mentioned above stopped; the apps not-responding while running a Windowed game still occurs but *seems* like it's much less often. So *maybe* an nvidia driver issue?
• Tried with GPU scheduling both enabled and disabled

 
I have NOT tried a clean reinstall of Win10 yet given I just ran the 2004 update which carries a lot of the same benefits but that is probably my next step. 

Did you do an upgrade in place? I've run into maddening problems with windows upgrades, and a clean install fixes them.
 
Edit: just saw the last line of your post. If you have a spare/old drive, you can just disconnect your current boot drive and install it on the spare to test.

I reseated all devices during troubleshooting. I failed to mention this. I basically broke it all down and put it back together and ensure both nvme drives had a snug connection. I think I may have deleted the dumps but the BSODs haven't occurred for several weeks since I set power mgmt to high performance. Though I'm not readily tracking with the immediately dismissal of power mgmt being the cause? If a game is set to high perf, then the game is minimized but GPU is still drawing X amount of power and the focus is set to something where the power mgmt setting is adaptive or optimal power, couldn't that lead to a the GPU being starved of the power it needs? Though I certainly agree it was related to hardware. 

I let memtest pro run for 12 hours. 0 errors. 

for best in-place Win 10 update experience - go offline & remove 3rd party security software First
 
I prefer the clean install from USB route

I am On a X299, and haven't had any issues with the New Windows Update, Because Windows keeps telling me my system is not ready for it..... and that I will get it when I am. This is a brand new build, Nothing was on it but the Old windows 10, (1909)  any Updates it wanted after the install, Installed from a USB Drive, Purchased directly from Microsoft, the drivers from the EVGA disk, the Newest RST drivers, and the Samsung 960 EVO driver.  It goes through every step, checks my system, down loads the Update, attempts to install it, completes and says checking for updates, Stops, and says it cannot be installed, But windows is working on it, and I will get it when my system is ready.
I have no idea what the issue is. X299 FTW K, with a new 9980XE. The New Windows 10 made it onto all my X58 systems without issue, and seems to be running fine.

 To be Honest with you, The only unusual settings I have, that I know of, are Three SSD's in Raid 0 for my system drive, and Two 2080 super black gaming in SLI, (or Rather NV-Link)

The only issue I have had since updating to 2004 (19041) is that my Soundblaster Z 5.1 speaker configuration keeps breaking.  The speakers go out of synch every so often and I have to repair the drivers and then reset the volumes, eq and such.  So far...I have done a clean install and a repair...both worked.   There is a thread on www.guru3d.com that talks about 2004 breaking Creative Control panel...others have had issues with sound as well.

Monstieur
Windows 10 20H2 is out in release preview, which is most likely RTM. You can try installing that instead of wasting time debugging 2004.

A very good idea and if you're willing a fresh install of the new build might be worthwhile. Don't forget to make a backup beforehand!