The main thing for that project was a focus on backing up the story telling. That is unusual in game effects since effects are normally driven by gameplay aspects.
If you are planning to do something like this, you need to think about how the effects can accentuate beats in the story and call out moments of contact between two characters, possibly when they really connect in the dialogue. You also need to think about if the effects should feel frantic for the moments in a scene or you can slow down the effects for more quiet, reflective moments to allow acting to shine through and not allow the effects to be distracting.
You are right with most guesses. There is the ribbons around the characters that helped define where they were and also gave them directionality when the characters where moving around. The bloom around the characters was also part of the same effect as the ribbons. Think they were partly setup in local space.
There was effects emitted from the character meshes (outlined in the second blogpost), that gave glimpses of the characters. I chose the poses based on key moments in the audio/acting that suggested a defined pose for the character. There was markers in the audio files with specific names for triggering the effect emission on different poses. This really helped in speeding up timing of the flashes.
It was a good while ago, so probably the blog posts would be most help to you.
Hopefully that helps a bit.