You can add additional memory stick if you'd like.  It is recommended to stay with the same brand/model for all 4 sticks, but you can mix and match. Depending on the manufacturer, some sticks can be compatible and some note. Note that adding more sticks will lower the overall DDR5 speed.
the 8950 came with 32 Gig of RAM (2X16) and I would love to double that or increase it for video editing.  I don't see where Dell configurations mention a 4x16 gig or even a 2x16 PLUS a 2x32 (for a total of 64 or 96 gig  respectively).  Crucial seems to be a viable choice for the 8950.  Anyone else do similar or see any issues?
XPS 8950, adding RAM