Best way to download our own TikToks clean for reposting as reels?

whatever you do, don't post the version with the TikTok watermark. Instagram has said it shows recycled content with other apps' watermarks to fewer people, so a watermarked repost starts at a disadvantage. If rebuilding isn't possible, cropping the watermark out usually looks worse than just remaking the video.

Going forward, export the finished edit to your camera roll before you hit post, so you always have a clean file. That one habit fixes it. For the old ones edited inside TikTok, there's no clean in-app download. Your options are the third-party downloaders, which are a bit sketchy, or rebuilding the edit from the raw clips if you still have them. For your best performers I'd rebuild.