Precision 3460 SFF - M.2 and SSD Accessories

We have just ordered a Precision 3460 SFF.  

Does anyone know: 
 * if there is a standoff and screw present for the 2nd and 3rd M.2 slots, if not what sizes
 * if there is an SSD\HDD tray present and for what size
 * what tray part numbers would fit this computer to hold one or two 2.5" SSD

 * What else I do not know to ask about adding storage

Can someone please help me understand all the Dell "Class" reference to NVME drives.  There are no class references on marketplace products.  Is there an article on this somewhere?

Thank you