[NAME]  Normally you only change that setting before reinstalling Windows (or whatever OS you want to run), since as you found, changing that setting to another state and trying to use an OS that was set up to expect it to be in a different state doesn't work.  But I've read that if you boot Windows into Safe Mode once after making the switch, you would be able to reboot normally going forward.  You just need to let Windows completely boot once in Safe Mode.  If you have trouble setting up access to Safe Mode, try switching back to RAID mode temporarily to get back into Windows, then prep for Safe Mode, then switch to AHCI, then boot into Safe Mode, then reboot into normal mode.
In order to install Ubuntu alongside Windows, I needed to disable iRST. After that,  Windows stopped booting. There was a warning about it so it's not a complain since Dell officially doesn't support dual booting. I just wander if it is somehow possible and boot Win 10 without iRST. I have a new XPS 17 2020 with 1T SSD.
Help needed , Windows doesn'r boot after disabling Intel Rapid Storage