As for the tie thing, there’s a balance between looking menschlich and between jewish pride and the Jewish look. So the older chassidim belong to a time where if you didn’t wear a tie you were seen as uncivilised and not a mentch.
So the Rebbe wore and shluchim wore but when an eltere chossid wore to a farbrengen, the Rebbe said you’re wearing this rag too?! And encouraged him to take it off.
At the same time shluchim don’t try to look cool and trendy at all. Full beard dress code etc.
Younger shluchim live in an era where formality is down the drain and ceos wear torn jeans. So some feel a tie is unnecessary veltishe hanachos and they’re fine without