Why?
What is the purpose of this project?
Specify how high resolution you need, and what do you need to do with the pictures once you take them.
What should be displayed on the screen and why does it have to be 7 inch?
Why micro SD?
The purpose of device is to record a person activity who will stand in front of the device and send the data to a web server.
RFID used to identify the person which will present his ID card. The camera will take a short video for the person while he is performing the activity. The monitor will display instructions and feedback until the activity is complete.
Micro SD is to buffer the captured the video before sending to web server.
Ok. You will not be able to use Arduino for video processing. It's just not powerful enough. I would suggest a cheap PC (or Raspberry Pi) and a web cam for taking and uploading the video.
Arduino can deal with RFID and display.