Need clarification on 2 matters

1) Do citizens change ideology over time or is it set when a new citizen appears and doesn't change anymore ? If it changes over time, what affects the chances to align with a particular ideology ?

2) I adopted Terror stars ideology from Nihilism tree. The part where it says I can construct (after researching) star killers is clear and straightforward. But it also says "Enhanced cosmic weaponry and stellar fortifications". What does that mean, - a new tech\passive bonuses\modules ? I haven't noticed any of that. There is a part about enemies fearing us. Does it mean something in practice even ? 
I think, more detailed description of ideology bonuses is very much needed.