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1) RSSI is the RECEIVED Signal Strength Indicator , the signal strength varies based on the output TX power set by you.
2) Yes , you can use a UART SCB component in your project to send the data to serial terminal. Also you need an external UART-USB converter. If you are working on PSoC 4 Pioneer Kit , the on board kitprog will do the UART-USB conversion. If you are working on your custom board with only PSoC chip , you have to use a external UART- USB converter ( KitProg, FTDI etc).
Potentially, you can setup an RS cable to receive the UART and spit it to the PC, but that will take about as much work as a UART-USB converter setup.