Can I control relays through an Arduino while using USB joystick?
Afaik USB on an Arduino is not really easy to accomplish. The USB is normally only usable for uploading a sketch and trace (RS232) data. Not to be used as a specific USB device. There are people who upload special firmware to have the Arduino used as USB device but this is not something for a beginner.

A camera with an Arduino is quite impossible, especially if you want to process the data from that camera on a microcontroller. You might take a look at a Raspberry Pi instead, afaik it also has a HDMI output.