Let me comment that programs like GeForce Experience seem focused on accommodating single-card users. Also, there is a hitch to installing NVidia drivers for 2x SLI or greater.
When installing the drivers, turn SLI off. After the drivers are installed -- and ALWAYS, ALWAYS do a "Clean Install" -- and after all the scheduled reboots have completed, turn SLI back on.
Some symptoms associated with an SLI-enabled driver installation include excessive power consumption at idle. That is, the full-bore P0 may drop back to P2, but it will not drop to P8 when the graphics cards should run at idle speed.
It is also possible to overclock SLI configurations excessively. A single card may overclock to a certain core and memory speed; dual cards might mean you settle from something slightly less than single-card speeds. And you might need a little extra voltage.