that asks you to "Install a Codec" or "Run the Setup" to view the movie: Stop immediately. Movie files should be playable directly. Prompts to "Install to view" are almost always malware or adware
The x264 encode preserves the desaturated, dizzying heights well, without significant "banding" in the blue sky.
This tells you the source. A WEBRip is captured from a streaming service (like Netflix or Amazon). Unlike a WEB-DL, which is a direct download, a WEBRip is often "re-encoded," which can lead to a slight loss in quality. DD5.1: Stands for Dolby Digital 5.1 surround sound.