The Definitive Edition was essentially the Original Edition + all DLC + the HR Texture Pack + some lighting tweaks. While the lighting in the Definitive Edition is sometimes criticized for being too "washed out" compared to the vibrant Original release, it is the easiest way to get the high-res textures without managing separate files.
To force the game engine to load the HD pack: The Definitive Edition was essentially the Original Edition
This version requires the separate "High Resolution Texture Pack" to enable HD assets. 2. How to Enable HD Textures (Definitive Edition) The Definitive Edition was essentially the Original Edition
You need a graphics card with at least 2.5GB of VRAM (3GB recommended). If you run this on a 1GB card, Sleeping Dogs will stutter or crash to desktop. The Definitive Edition was essentially the Original Edition