Regarding long/short jackets – yidden did not dress like goyim abd merely copy their fashions. The yekkies were so called and criticized for changing their dress simply because the German goyim switched to short jackets. The rest of klal yisroel for many decades maintained long jackets, in Europe, sefardi countries, and yerushalayim. With the winds of haskalah, the litvishe caved and helavei it was the worst thing we did…be’avonosainu horabim it was around that time that the women stopped covering their hair, largely for the same reasons.
Rav shach in a parshah sefer called “merosh amanah”( i believe this story is found there, if not it’s in a different anthology) told
a chasidishe bochur in ponevezh yeshiva was having a hard time in shiduchim, because while he dressed chasidish, he was more aligned with the litvishe hashkofah and wanted that lifestyle. Litvishe girls didn’t want him, and chasidishe girls weren’t a fit. He asked rav shach if he can change to short jackets, and rav shach told him that there’s not a chisaron with short jackets – the olam hatorah wears them. But there is a maalah, an advantage in long jackets. They are a higher level of tznius, so changing for the sake of shiduchim isn’t valid hishtadlus, since it involves a slight yeridah. It’s like how rav moshe feinstein ruled that a shul with a balcony for the women’s section cannot change to a same-floor divisiob, since it’s a yeridah – it’s not bad in itself, but we don’t go down in kedushah, we only go up when we’re able to.