When I was using qBittorrent in a container in a Rasperry Pi 4, it was definitely the raw power that’s was throttling my downloads. You may wanna check CPU usage, specially if going through a VPN.
Also try limiting the maximum number of connections and slots for download and upload. You want to connect to less people but still use the same bandwidth, which is basically transmitting more data to those people.
How are you “among the firsts to get a torrent”? In private trackers, people use special software to be the very first, and on top of that seed-boxes with 10, 40 or even 100 symmetrical Gbps. Check “autobrr” to get started. It is not uncommon that you for example reupload a torrent from other tracker to get some sweet ratio and somebody cross-seeds your torrent and starts uploading before you.