1) If someone's personal minhag is not to say Yotzros and he finds himself in a Shul that says them, he should not be "Poresh Min HaTzibur, deviate from the congregation" and he should say it along with them. (See Rama Siman 68 and Siman 90:10)
If for whatever reason one is not saying them, he should just wait silently while they are said by the congregation and not talk , even words of
Torah, and certainly not make light of these extremely exalted Tefilos which contain in them great praises of Hashem as well as many wondrously holy and deep Kabalistic concepts. (See Kav HaYashar Perek 86)
2) These Tefilos should be said clearly, with extreme Simcha and concentration, and should not be said as if it is a burden to say them. Many of these Tefilos were authored by holy Tanaim, Geonim and Rishonim with the input and advice of heavenly angels. (ibid.)
Saying these Tefilos are a Segulah for Arichas Yamim (long life), and those whose familial or congregational minhag it is to say them, and they don't, place themselves in danger. (See Kav HaYashar ibid., Bach Siman 68 Dibur Hamaschil UMah Shekasav Amnam and Shu"t Bais Hillel Siman 71. See also Pri Megadim;Mishbetzos Zahav, Siman 53:10 that saying these Tefilos are a Segulah to bring our as yet irreligious brethren closer to Hashem)