When do Yekkes first don a kittel?
from Mi Yodeya
What I'm gathering from various places is that most Minhag Ashkenaz wear the kittel and tallis during schacharis on RH. But not during Maariv or Mincha. On YK both are worn for all tefillos. As for the white yarmulka and tie, I believe, but am not sure, they are both worn for all tefillos.