This is a partial answer. I will give a quote from Sri Ramakrishna on Sandhya.
Sri Ramakrishna said: "When, hearing the name of Hari or Rama once,
you shed tears and your hair stands on end, then you may know for
certain that you do not have to perform such devotions as the sandhya
any more. Then only will you have a right to renounce rituals; or
rather, rituals will drop away of themselves. Then it will be enough
it you repeat only the name of Rama or Hari, or even simply Om."
Continuing, he said, "The sandhya merges in the Gayatri, and the
Gayatri merges in Om."
The Gospel of Sri Ramakrishna, chapter 1, Master and Disciple
It seems from the above passage that a sanyasi will not have to perform such rituals as he makes spiritual progress.