Download gpu-z, run it and take a look at memory size, it will show how much ram in megabytes is on each gpu (you can change gpu's at the bottom drop down menu), it will also list here (among complete specs of the card) if sli is enabled...
It lists an nvidia card with that model so if you right click on your desktop and select Nvidia control panel, in the Display list is an option to adjust desktop size and position, partway down this list is a dropdown for "Perform scaling on", choose "display" instead of "gpu" with the external...