You don’t need to download ProtonAOSP yourself in most cases. Use the web installer instead to install it quickly and easily. It takes as little as 4 minutes, depending on the speed of your internet connection, and is safer than manual installation; see Installation for more information and common misconceptions.
Variants with gapps include Google services and apps necessary for most popular apps to work, including the Google Play Store. Minimal variants lack support for such apps, but they are more privacy-friendly.
The following downloads are for the latest public version, 12.3.2.
Factory images can be flashed the same way you would flash stock Pixel factory images from Google. Check the manual installation guide for instructions.