SATA 2.0 to M.2 (NGFF) design
So I finally came with the solutions : 


I checked on some boards to see if it matched and it does.
Got feedback from Allwinner engineer, differential pairs should be controlled to 100Ohms +-10%
I found that the screw hole center on the NGFF PCB matches the edge of the PCB. And it's exactly at 42mm (for 2242) from the other PCB edge.
So in order to put the screw hole on the host PCB I checked the connector drawing to find out where the NGFF PCB starts compared to the connector layout. Then added 42mm.