R’ Chaim Kanievsky has letters printed in a few seforim where he says that it’s better to daven b’yechidus with a hat & jacket while R’ Shlomo Zalman Ztz”l held that it’s better to daven with a minyan.
As far as bentching is concerned, I do not remember the exact nusach but the Mishnah Berurah says something to the effect of “tov” or “nachon” to wear a hat & jacket when bentching.