Thank you! Well, there were few things that i think were crucial to the artstyle, and i'm thinking about posting a post-mortem in the near future to tell about the process in a more detailed fashion, but basically:
1. Low resolution textures with decent pixel art
2. Low polycount on 3d models
3. (World) camera renders to a small resolution texture, that is then scaled to the screen size (in this game it was 480x270px, firstly 384x216px)
4. Every texture had no filtering (bi-linear, tri-linear etc.) - in Unity you can use "point filter" -option
5. Use billboarded (pixel art) sprites as 3d objects (such as the hands or NPC's in this case)
There was an actual vertex displacement shader for simulating the PSX-like vertex "twitching" effect, but i scrapped it, because i couldn't make it work with shadows and lights other than vertex lit - and it looked like crap compared to the current way of doing it.
I added some bloom, grain and chromatic aberration as post processing.