I remember hearing rav berel wein discuss this topic.
He did claim that the early mekubalim had very short peyos.
This includes the arizal and his beis medrash.
I know he also mentioned the ramchal as well.
He claimed that they were worried about accidentally plucking peyos hair.
He mentioned the famous story of the Steipler won touched his beard on shabbos and kept it there until motzei shabbos, or of coven for accidentally plucking hairs on shabbos.
He claimed the early mekubalim were worried about this all the time for kabalistic reasons, so they kept it short.
He also mentioned that rav Moshe Feinstein zatza’l said that he kept his peyos long and behind his ears only because otherwise, if he had short peyos, certain kehillos wouldn’t respect his piskei halachos.
He felt it was important for a manhig to have certain standards since it’s important that klal yisrael respect its manhigim, and part of that is maintaining a certain “tzurah” (similar to wearing a frock and hamburg).