When Imam recites Ayate Durood after Jama'at the followers (Muqtadi)
priase Durood aloud. Due to this some people say that since you
say durood aloud you should also say Aamin aloud after Surahe Fatiha.
So what is the Shara'i Verdict on such people. Some people do not
say Aameen at Imam's Dua but they say their own duas quietly. So
the followers (Muqtadi) should say their own dua or say Aameen on
A: If Muqtadis praise Durood or say Ameen with such intensity that it breaks the concentration of other people who are still praying Namaz then it is definately not allowed. If some one does that then it is given that he should be stoped forcefully, such is mentioned in Fatawa-e-Rizvia in part three on page 596. Therefore if they (who question loudness) say because of this reason then they are right (on Haq) but if no one is praying Namaz at those times than it is permissible to be aloud.
Dua is definately Amre Mehmood (likeable deed). However performed, it is allowed. ALLAH Ta'ala says 1*. But is better to say Aameen at Imam's Dua than perform Dua alone. Because if mutiple people would say Aameen at Imam's Dua then Dua will be Aqrab Baqabool (better chances to come true). Alahazrat Imam Ahmad Raza Muhadis-e-Brelvi radiallah anhu writes,"There is blessing in Jama'at and Dua of a group of Musims is Aqrab Baqabool. Scholars mention that wherever there are 40 True Muslims gathered among them one is a Wali (ALLAH Tala's beloved) for sure. (better chances to come true). Fatawa-e-Rizvia, Book 9, Part one, Page 157.
Allah Ta'ala Knows the best.
24,Soorah Momin, Ayah 60