All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Straightening the rows and standing side by side (shoulder to shoulder and foot to foot) is a recommended act. However, if exaggerating in doing so harms some people who do not know the Sunnah, then this matter can be avoided until they know and understand and until the Sunnah is clarified to them. Nonetheless, you should still be keen on straightening the rows, but in a manner that does not lead to any disadvantage (dispute).
Saying Aameen silently is the view of some renowned scholars, and there is no harm in acting according to it if the contrary leads to a disadvantage.
As regards saying “Basmalah” (Bismillaahi Ar-Rahmaani Ar-Raheem) aloud or silently to yourself, then the matter is easy and can either say it aloud or silently, and there is no harm (or sin) in whichever choice you make. However, you need to be mindful of the general interest of the congregation when making your choice.
In any case, Shaykh Ibn Taymiyyah and many scholars stated that there is nothing no harm if one foregoes some recommended acts in order to soften people's hearts (i.e., unite their hearts). Their evidence for this is that the Prophet refrained from demolishing the Ka‘bah and rebuilding it based on the foundations laid by Prophet Ibraaheem (Abraham) because the Quraysh were new Muslims, and other pieces of evidence.
For more benefit, please refer to Fataawa 331852, 347506, and 340912.
Allah knows best.