Minhag ashkenaz would mean of German origin, not jut someone who davens nusach Ashkenaz. The GR’A and those who follow minhagei HaGR”A do not ear tefilin even though they daven nusach Ashkenaz. This why you almost do not find people in EY wearing tefilin on chol hamoed.
Vilna was in the heart of Lita, so saying it is a “litfish” minhagg is stam shtuyot.
Chasidim who follow minhag Sanz wear tefilin on chol hamoed either until they are 18 or they are married (there are slight differences in different chassidus)