I've been using Linux for 6+ years, and I'm still very confused about how Linux handles it's file system and partitioning. So don't feel too bad, after all, I just delivered a rant recently over it lol.
I too used to be a Windows user, so I know all too well how you mean. Windows made it easier in that regard. Linux is unecessarily convoluted in this area.
I'm glad you figured out the auto mount in DISKS. I've had to give this instructions on the forum countless times to users.
Also NVME is handled differently then standard SATA. NVME requires its own controller to drive it. It's seen a bit different by the system. So it's handled a bit differently.
I'm going to bed and don't wish to type all night on a phone screen keyboard. So this is all I will say. I just wanted to acknowledge you and let you know that you are heard and understood.
Goodnight 

My other current one is about changing the drive where the Desktop is stored and whether I need to reset ownership and permissions on that drive. Then I can move on to the fun of changing the file manager - Nautilus seems far inferior to Nemo and Thunar. (Whereas Dolphin seemed worse.)