You shouldn't be running it in AHCI mode, that's a SATA thing. It should just be NVMe mode with RAID disabled. It looks like CrystalDiskInfo is showing it running in NVMe mode, so it could just be confusing wording in the BIOS or misunderstanding what the BIOS settings are saying. If it somehow is in AHCI mode, that would certainly cripple performance:https://phisonblog.com/ahci-vs-nvme-the-future-of-ssds-2/
Did you "secure erase" the drive after changing the config and before reinstalling? There's probably an option in the BIOS Tools menu to do that. That resets the drive, and marks all of the cells as empty, similar to TRIM. It can't undo the lifetime data written / wear, but it's as close to a factory reset as you can safely get as an end user.
You could try a quick ReTrim in Administrator PowerShell, see if that improves things.
Optimize-Volume -DriveLetter C -Analyze -ReTrim -Verbose
That's non-destructive and just issues TRIM commands to the drive for all of the NTFS free space. Modern SSDs are supposed to be more tolerant of not being properly trimmed, but it has been known to hurt performance in the past. It's kinda the SSD equivalent of defragging, but very quick and doesn't move huge amounts of data around.
You should install AData's SSD Toolbox, and run their diagnostics on the drive, see if it shows any errors or problems, and check if the drive's firmware needs an update:https://www.adata.com/us/support/consumer?tab=downloads