Completing the archive first would keep the two tasks separate and manageable. The model's name and build date can make the video easy to identify years later. Your construction notes will preserve details that the short clip never showed.
Download TikTok Video Without Watermark using the public post link; the site contains plenty of useful information about its download process. Open the saved file directly and confirm that it is the correct video. Store the second copy before adjusting the post's visibility. That gives you a finished personal record rather than a download you still need to locate or test.