The PSREF document that Lenovo produces, so I would say that if you do not want to experiment (expensive!) that you should accept PSREF.
I have a Lenovo X1 with a 1 TB NVMe SSD drive and (a) I ordered it from Lenovo that way and (b) PSREF said 1 TB Max.
I got an M70 Desktop and it allows a maximum 1 TB for the main drive, I got one from my supplier and it is the same drive as the X1 . Webpage
So I expect the basic BIOS (UEFI) dictates what is the maximum disk drive and maximum memory. PSREF normally reports that very well.
Since Lenovo issues the BIOS (UEFI) updates, they really control the maximum size of devices.