The system won't take an M.2 SATA drive -- that is correct.  But it's also not going to be limited to 1 T for NVMe/PCIe, either -- you can install any drive that physically fits into the system.  
I have a 512GB SSD M.2 (I think PCIe) installed in my 3510 and need more storage space.  I see the following specs in the manual: Feature                   SpecificationHDD 2.5 inches     Up to 1 TBSSD 2.5 inches      Up to 360 GBSSD M.2 SATA       Up to 512 GBSSD M.2 PCIe        Up to 1 TB It does not seem like I can install a SSD M.2 SATA under the M.2 PCIe, is this correct?   With the M.2 drive installed, I followed this article on installing a drive in the 2.5-inch bay: [URL] In which case I have to install a M.2 drive there. What are the size limits for it? Can I increase this with a BIOS update?  Thanks for any help 
Precision 3510 storage specs