You can use GPU-Z or MSI Afterburner to see what load is on your GPU - I have an old monitor as second screen and have those plus Core Temp running on it to see CPU and GPU load and temps on it while game runs on my main screen- you can force it so SLI in AFR mode - splits load to about 50% per GPU for me, but it's about 2 or 3 FPS less than single GPU - though does keep the temps down on GPU#1 as it running less load
