Things I have learned:
1) Modern Standby in both Windows 10 and its implementation on Dell laptops is the work of **bleep** himself. It is simply useless, you can never be sure your system is truly sleeping and it may wake up randomly in a bag and heat up dramatically at any time. The web is littered with horror stories.
2) My issue is categorically due to the audio driver, Dell's latest supplied version just doesn't work, I can temporarily fix it and get around 0.5%/hr battery drain and actually enter DRIPS state by using the 'wrong' driver, ironically by going through Windows Defender and identifying a driver problem there. However at some stage it will revert back to "Smart Sound Technology (Intel (r) SST)" and then your laptop becomes a desktop again. The audio driver will prevent sleep state and be active 100% of the time, keeping the system more awake than it should be (no DRIPS). It shows up red on a powercfg /sleepstudy report and can easily be identified.
This might or might not be related to the 'crunchy' sound on most system audio events, but that's the least of my problems with this laptop.
I haven't turned my system on for a few days so I will be checking it today. I did find once that using Edge would cause extra power drains on my system. Using the Task Manager to end that task may help some.
My audio notifications sounds are delayed and can be slightly distorted just if the system has to turn it on. If I test the sound more that once, the next time it will be on time with no distortion.
I will get back after my system operates for a few hours but we still have your situation of no hibernation to deal with.
I have checked my systems through several Modern Standby situations and nowhere are the Intel SST Audio mentioned.
I even enabled Cortana to hear me but my system will not turn on the Display using Cortana. Yours may turn on since it is one of the activities Microsoft was saying worked.
There was just another poster asking about the Bios on the 9365 who seems to be getting several systems. Maybe you could consult with that poster and compare capabilities.
Modern Standby is a horror story. Dell is even saying that "putting a laptop in your bag while it's in Modern Standby will void the warranty." which is absurd.
Best solution I've come up with after months of pain is to just disable the garbage in the registry and force S3 sleep.
Sometimes the graphics driver glitches after resume, but at least the machine sleeps properly now.
Closing this out, the latest round of driver updates finally seems to have 'reasonable' (1%/hr) battery drain restored and a sleepstudy report shows largely 'green' results with some active time in DRIPS. Fingers crossed this remains. At least I can get a couple of days in standby instead of just overnight.
Could have been any number of things I tried related to removing/deleting/disabling audio devices, but also noticed a BIOS update recently. That and the Intel chipset/thunderbolt driver set seem to be most likely culprits.