In many of His incarnations, Bhagavan would not have revealed all His aspects and instead would be in the form of a human or an animal; only in His incarnation as Krishna, did He reveal all His Supreme Being aspects.
Both Vishnu and Narayana are the same. Between Brahma and Shiva, Vishnu is another incarnation.
Swami Narayanan tradition could be an offshoot of Vishishtadvaita tradition. But both tradition and principles are different. We need not follow them.