Once Pokémon spawn around you in the overworld, their stats are already determined.
While PID, IVs, EC, Height, Weight could not be viewed (apparently generated from some kind of set seed), other details can be seen.
This is just a viewer, not an editor.
It reads the kcoordinates block exported from PKHeX.
You're also gonna need to download this file, specifically the 32-bit version: https://www.microsoft.com/en-us/download/details.aspx?id=13255