I just purchased an Optiplex 7060 Micro with 256 NVME SSD preinstalled. I added a Samsung 850 EVO SSD to the computer. I noticed the SATA mode was set to Raid by default in BIOS. In the Samsung Magician software, it shows  AHCI is deactivated. I tried to reset the SATA Mode to AHCI, but the computer does not boot. I have to change it back to raid mode. I have a few questions:

1. Does the raid mode have the same performance as AHCI mode for 2.5 inch SSD? 

2. If I change the SATA Mode to AHCI Mode and reinstall windows 10, will this change affect the preinstalled M.2 slot NVME SSD performance? Or the SATA mode change does not affect the M.2 slot?

3. What is the best setting for this situation? I have no need for RAID. I just need another SSD to get bigger storage.  

Thank you for any suggestions.