Was just talking to someone on Reddit about the possible impact of Ron's encounter with the brains in the Department of Mysteries.
Could go a slightly Lovecraftian route where the brains don't "give" him anything, strictly speaking, bit they twist/crack his brain's perception of reality, maybe something like genuinely seeing the world through the eyes of the people the brains used to be.
By that I mean, to perceive reality as if you were another person. Through their eyes, in their skin, feeling their thoughts and emotions as if they were your own, and not just "as if they were your own" but completely eliminating all sense of borders, of definition, of separation between the self and the other such that, in the moment, the conscious mind draws no distinction between the reality experienced by the self and the reality experienced vicariously through the brain. In the moment, Ron wouldn’t be able to tell which one was real, or even which one was truly him.
This experience, especially with multiple brains at the same time, would forcibly alter his perception and perspective of reality. He might gain some of the instinctive wisdom that comes with having experienced the lives of those other people. He might undergo a crisis of identity as leaves the brains behind and realizes that his own experience of reality is no more unique or special than anyone else's. He might gain an advantage in empathetic scenarios due to having experienced a form of true empathy, literally experiencing someone else’s reality, that no one else ever has. He might even gain an advantage in certain types of magic, magics of persuasion or illusion, things that rely on blocking, enhancing, or altering the perception of reality by the self or another.
It could be something like the Overview Effect experienced by astronauts, who go into space and look down on the Earth only to see it completely without borders, distinctions, or any of the arbitrary separations of society.