HEIC vs WebP: which should you use?
HEIC (based on the HEVC video codec) is an excellent capture format and Apple's default since iOS 11. Its problem is reach: it is patent-encumbered and unsupported by most browsers and web platforms. WebP is royalty-free, supported by 97%+ of browsers and accepted by every CMS. Keep HEIC in your camera roll; publish as WebP.
Converting on Windows or Android
Because only Safari decodes HEIC in the browser, users on other platforms should first export the photo as JPEG (Photos app → Share → Options → Most Compatible, or via iCloud.com download) and then use the JPG to WebP converter.