Avira,
Litvishe Yeshivot – a good point that their regular clothes were due to self-confidence. Possibly also because Lithuanians did not represent a cultural challenge the way Poland or USA do.
A good idea to look at Rambam! In Deos 5:9, he is saying this about clothes:
clothing should be attractive and clean… no stains ..not wear regal garb,.. nor the dress of the poor which shames its wearers, but attractive garments of the middle range.
flesh should not be visible … should not drag on the ground
dress as befits [his income] (not more or less)
I don’t see anything here about being different from others – respectable and middle class. British suit sounds good – if you can afford it.