My 13" 2014 MBP supports 2 mDP + 1 HDMI = total 3 external displays.
Running external display at 4k@60Hz is possible but not straight forward, it requires patch core graphic framework, or using 3rd party boot loader. Newer models do not have this limitation afaik.
https://www.apple.com/macbook-pro-13/specs/
People have gotten round it by connecting additional screens using display link adapters.