The card is expected to have a layout similar to the GTX 960 reference design, with three DisplayPorts, HDMI and DVI outputs. Performance-wise the GTX 950 is expected to target AMD's Radeon R7 370.
GeForce GTX 950 will be available in two configurations: 2GB and 4GB of GDDR5 memory. Although unconfirmed, it looks like GTX 950 also has 128-bit interface (judging from memory capacities). That said, GTX 960 and GTX 950 should only differ in CUDA count and clock speeds. More details will be available soon.