According to the technical product specification of this device, the maximum resolutions are the following.
1) 4096 x 2304 @ 24Hz using the mini HDMI.
2) 3840 x 2160 @ 60 Hz using the mini display port.
It is possible to get these resolutions using high quality cables (HDMI 1.4a and DisplayPort 1.2)
For dual display and three monitors, please check page 22 of the TPS
http://downloadmirror.intel.com/24794/eng/NUC5i7RYB_NUC5i7RYBR_TechProdSpec02.pdf
Mike C