Total speed is going to be bottlenecked somewhere, which could be drive read speed, upload bandwidth, or the peer's download speed, their write speed, or any number of other factors.

If your side is capable, don't worry too much about it. You could be seeding to someone on their phone in a shack in remote Mongolia. That's never going to be fast.

Also, reset all the advanced options back to default. You don't need to touch any of them, and changing things might make it worse.

Don't know if this helps you but did you already try changing Disk IO Type to Simple pread/pwrite (in advanced settings)? It was meant to address some issues with disk read/write + RAM usage. Not something that affected me all that much but could be worth a look.

Was mentioned in the 5.0.1 release notes and in the github pages

https://www.qbittorrent.org/news

https://github.com/qbittorrent/qBittorrent/pull/21300

Beyond that I'd echo the other comment, try to just change settings you actually need to change. Oftentimes people make a whole ton of settings changes in their torrent client and then can't figure out how to get it back to normal.

If you're seeding more than one file to more than one concurrent user, chances are, your drive needs to switch around and buffer quite a bit left and right to get the material you're seeding cached. That sounds like fairly formal behavior.

I think it's just normal, I seed from a 10gbps SSD and barely get above 7MB/s