What is the Halachos for men regarding Tznius Like shorts, Covering parts etc.
The clothing of a man should not be provocative or demeaning, certainly the clothes should not be tight that could cause friction to the “Erva” area.
One must also follow the standard custom of the locale.
One must wear pants (not shorts) and that they not be very tight, as is the custom among all G-d fearing Jews. The Rebbe was very displeased with seeing a picture of a man wearing shorts in a bungalow in the summer.p and he spoke about it with great anguish. See Sichas Shabbos Terumah 5741.
In regard to Tefillah, one should dress like one is preparing to greet the King.
See also here and references
Rema (Even Haezer 23:6).
Shulchan Aruch Orach Chayim 91:5-6.