Regarding the "bragging" posts, according to this Hidden Brain podcast [1], it has a more negative effect than anything and is usually not the truth about people current situation in life. For instance, we might see the great vacation pictures, but turns out they were fighting the whole time and it wasn't fun at all, but it is not like they are gonna share that part on FB.

[1] https://www.npr.org/2017/04/17/524005057/when-it-comes-to-ou...