Problem with bitrate limit affecting transcoding bitrate

[flo f]

Let me try to summarize what you want:

1. You have a good upload speed, but the Jellyfin server's hardware has poor performance.
2. You want to utilize the upload speed, but when transcoding media that cannot be played directly and needs to be transcoded, your server cannot keep up with the high bitrate.
3. Now, you want a feature to throttle the transcoding bitrate only while keeping the network speed bitrate unaffected.

If you are not using hardware transcoding of any kind, you can set the CRF value to an extreme high value (like 50) and see if the makes the situation better.

You can also try to change the Encoding Preset to ultrafast.

Yes you're completely on point, this is exactly what I meant. 
I'm using hardware transcoding, but only to decode the HEVC, not for H264 encoding, because that is not supported (or so I thought from jellyfin documentation, where I remember reading that there is almost no hw that supports it). That's why I thought I could still use CRF and Preset, but it doesn't seem to be doing anything, like I mentioned in another Thread: https://forum.jellyfin.org/t-do-the-tran...ually-work

Like I said there, the preset doesn't seem to help even if set to the fastest setting. My settings are:

HW acceleration: Intel QuickSync
Hardware decoding: VC1, HEVC 10bit, VP9 10Bit
Prefer OS native DXVA or VA-API 
Options:
Enable Hardware Encoding
Enable Intel Low-Power H.264 hardware encoder <-- is this the problem?
Enable Intel Low-Power HEVC hardware encoder

I'm a bit confused, because when I look at the performance during encoding, intel htop shows only 20% use, while all CPU cores are at 98-100%.

I'm currently checking out a workaround to store multiple versions of the same video, to avoid transcoding alltoghether. But I'd prefer to avoid having to do that.