RX LOs  independent? How many bits in ADC?

Rx channels share the same LO. They cannot be configured for 2 different frequencies. They can receive signals separated within 100MHz.

In AD9371 DAC is 14 Bit and ADC on receive and Observation path is 16 bits. You cannot compare performance with stand alone ADC as the performance you measure will be for full signal chain.

In RX only application, are AD9371 and AD9375 the same? Yes. The receive sections are same.

AD9371 is an RF to bits transceiver and the output of the chip is Digital IQ through JESD interface. What I understand is you are planning to replace AD9863 with AD9371 and feed a down converted 1GHz RF signal at its input.This approach is Ok,

Please note that AD9371 does not contain LNA and the interface to baseband is JESD. For more details please refer User guide UG-992 downloadable from below link. (register and download required package)

http://www.analog.com/en/design-center/landing-pages/001/integrated-rf-agile-transceiver-design-resources.html

Rx channels share the same LO. They cannot be configured for 2 different frequencies. They can receive signals separated within 100MHz.

In AD9371 DAC is 14 Bit and ADC on receive and Observation path is 16 bits. You cannot compare performance with stand alone ADC as the performance you measure will be for full signal chain.

In RX only application, are AD9371 and AD9375 the same? Yes. The receive sections are same.

AD9371 is an RF to bits transceiver and the output of the chip is Digital IQ through JESD interface. What I understand is you are planning to replace AD9863 with AD9371 and feed a down converted 1GHz RF signal at its input.This approach is Ok,

Please note that AD9371 does not contain LNA and the interface to baseband is JESD. For more details please refer User guide UG-992 downloadable from below link. (register and download required package)

http://www.analog.com/en/design-center/landing-pages/001/integrated-rf-agile-transceiver-design-resources.html