A. The answer depends on your communal custom.

Everyone agrees that we don’t wear Tefillin on the holiday days of the festival, which are the two days at the beginning and two days at the end (or one day at beginning and one day at the end if you’re in Israel). Those days are holiday days, and considered like Shabbat, and we don’t wear Tefillin on those days.

The question is only about Chol HaMoed, the intermediate days of the holiday. Literally, Chol HaMoed means the “weekday holiday” or a blend of both holiday and weekend. On Passover we still abstain from Chametz on these days, and on Sukkot we still eat in the Sukkah and shake the Lulav on these intermediate days. But work is allowed, we can drive, use electronics, etc.

The Sephardic and Chassidic custom is not to wear Tefillin at all on Chol HaMoed, and therefore no Tefillin at all for all of Passover and Sukkot. Ashkenaz communities do wear Tefillin for most of the morning prayers but remove them for the Musaf which is the last part of the prayer that’s distinctly for the holiday.