Both the URLs open the same page on YouTube and the full URL is always in the format - /channel/<CHANNEL-ID>. The custom URL can be modified by the channel owner but the Channel Id URL will always stay the same.

To find the URL of an embedded video, you can follow these steps: Right-click on the embedded video: If you are viewing the video on a website, right-click on the video player and select "Inspect" or "Inspect Element" from the context menu. This will open the browser's developer tools.

Another option is to use a file-sharing service like Dropbox or Google Drive to upload your video. Once uploaded, you can easily share the link with anyone by copying the file's public link from the sharing settings page. Whichever method you choose, ensure you create a link that's both secure and easy to remember.