Who are you including in "Bnei Ashkenaz"? Yekkes? Nusach ashkenaz? Ashkenezim?
What is your source for these different nuschaos and for their being "pretty much unviversal"?
Search Google for ליטא רייסין and you'll find selichos and machzorim, some will add זאמוט, some will add פולין, while the broadest seems to be מחזור כמנהג פולין, רייסין, ליטא, פיהם, מעהרין ואונגרין. I think these are what might be referred to. They all davened Nusach Ashkenaz before תלמידי הבעש״ט spread Chassidus.