Dual monitor on Macbook Pro Retina: difference between 13 and 15 inches?
HT5219 Thunderbolt ports and displays: Frequently asked questions (FAQ) says the 13" Retina Macbook Pro will happily run with two Thunderbolt displays.

Although I have not used it first hand, I would not expect you to have performance issues running the two extra displays. The main retina display is actually drawing 4 times as many pixels as the external displays, and then scaling the image down, so a Thunderbolt display is not going to make much of a difference.

As to the scrolling performance, I believe that was fixed in a software update