Which MCU (Atmel) I can use with QTouch library?
You can use QTouch also on MCUs which do not have dedicated touch controller peripheral attached to it. Although there will be some limitations like only one single sensing method can run at a time. Also, it will consume more CPU time and more power. 

Check out Atmel's site: http://www.atmel.com/products/touchsolutions/bsw/touch-support-for-mcus.aspx


  For devices without peripheral touch controller, Atmel offer a
  software based solution that allow high degree of freedom for
  microcontroller selection and configuration. Most Atmel AVR and SMART
  ARM devices are supported and the library provides robust and industry
  proven capacitive touch performance. QTouch library supports both self
  and mutual capacitance sensing. Unlike microcontrollers with hardware
  touch module (PTC) the software library is only capable of running a
  single sensing method at a time. A pure software based touch system
  will also use more power and CPU time than a PTC based system. Code
  development and debugging is made simple by QTouch composer which is a
  free extension to the Atmel Studio IDE software.