While 1080p and 4K Ultra HD are available, many cinephiles still opt for 720p (High Definition) for several practical reasons:
Since the trilogy’s original release, several high-definition versions have replaced old, low-res torrent files: The Criterion Collection (4K Restoration): Infernal Affairs Trilogy 720p Torrent
As for accessing the trilogy, I recommend exploring legitimate options such as: While 1080p and 4K Ultra HD are available,