Setting 1.1.1.1 as the DNS server on a router will simply use the Cloudflare DNS server instead of your ISP DNS server. It improves speed and makes it harder to the ISP to track your activity, or block sites for you. But still they still see to which IP addreses you are connecting to. And anybody with your IP can see what files you are torrenting (this can be checked at https://iknowwhatyoudownload.com/)
WARP will route all your traffic through the Cloudflare servers (like any other VPN). So your IP is hidden from the public when torrenting, and from the sites you visit. And your ISP doesn’t know what sites you are visiting
Your seedbox probably shares the same IP address with other people. So those xxx downloads are from them.
the DHT is just a decentralised torrent index that lists all torrents in public trackers, plus the ones seeded by people with DHT enabled in their client, iirc