If i’m not mistaken, the main minhag for bnei Chol is to say “tehillas H” (the last part of shir hamalos) before benching, whilst the main minhag for bnei EY is not to.
When a ben EY is in Chol, should he say tehillas H?
If the answer is no, is it permitted for him to do so? For example, when eating at a seudah where others do say tehillas H.
It isn’t the minhag of people in Chutz La’aretz, as most people in the states, Litvishe and Chassidishe don’t say it, (in fact many of their siddurim don’t even print it), rather it seems to be more of a Yekishe minhag. Regardless, the general rule of saying things when in the company of others that don’t have a different minhag, is that things one should say the things that are said quietly, but when saying things that are said out loud, then he should say like the local minhag. For example, when a person who daven nusach Sefard, is in a minyan that davens Ashkenaz, he should daven Shemona Esrei according to his minhag, but when a chazzan says chazoras hashatz or when the tzibbur says kedusha, it should be said according to the shuls minhag. Tehillas … is not something that is meant to say out loud therefore you can say it quietly when you are at someone else’s home.
Halichos Shlomo (Tefillah) 5-19 ftnt. 31.