The internal SSD socket specification

[Towaka]

Is the internal SSD socket specification for the HP Pavilion x360 Convertible 15-cr0011nr an “NVMe 2280 M.2 SSD” or a “SATA 2280 M.2 SSD”?
What is the maximum capacity in TB for that SSD socket?

[Towaka]

I found the “Maintenance and Service Guide” for the HP Pavilion x360 Convertible 15-cr0011nr (15-cr0xxx).
https://h10032.www1.hp.com/ctg/Manual/c05975208.pdf
According to it,

Storage Support for all 7.2 mm/9.5 mm, SATA, 2.5-inch:
Support for solid-state drive + hard drive
Support for M.2 SATA solid-state drive

Single hard drive configurations:
1-TB, 5400-rpm, 7.0 mm
500-GB, 5400-rpm, 7.0 mm

Solid-state hard drive configuration:
1-TB, 5400-rpm, 7.2 mm, solid-state hard drive with 8-GB NAND

Dual storage configurations:
128-GB, TLC, solid-state drive with 1-TB, 5400-rpm hard drive
128-GB, TLC, solid-state drive with 500-GB, 5400-rpm hard drive
16-GB, PCIe, 3x2, 3D Xpoint Optane solid-state drive with 1-TB, 5400-rpm hard drive

M.2, SATA-3, solid-state drive with Triple-Level Cell (TLC):
512-GB
256-GB

M.2, PCIe, NVMe, value, solid-state drive:
512-GB
256-GB

IMPORTANT: The solid-state drive is installed into the M.2 connector that is used by the Optane memory module. You cannot install both a solid-state drive and a Optane memory module in the computer at the same time.

Description Spare part number
512-GB, PCIe, NVMe                 L20840-001
256-GB, 2280, PCIe, NVMe   L20839-001
256-GB, SATA-3, TLC                L20838-001
128-GB, SATA-3, TLC                L20837-001

[tk_srq]

@Towaka,

As the manual shows, your notebook's M.2 slot supports both SATA SSDs and NVMe interface. NVMe SSDs are much faster than SATA SSDs. 

Your model supports the dual storage (2.5" HDD + M.2 SSD).

15-cr0xxx models support Optane memory which is the M.2 NVMe SSD. Optane is paired up with the HDD to create RAID volume configurations to accelerate the performance of the HDD. Newer laptops use M.2 NVMe SSDs instead of Optane.

Your best upgrade option will be to install an M.2 NVMe 2280 SSD and install Windows on it and use the HDD for data storage or remove it. 

You can use an M.2 NVMe SSD of any capacity you want, 512 GB, 1 TB, 2 TB or more.

Your M.2 slot is gen3. An Gen4 NVMe SSD will work but run at around gen3 speeds.