Recommendation for single slot graphics card

[TheDreadPirate]

What I need is single slot GPU, there is absolutely no space for more in my case. I wanted to buy an nvidia T400 card but the guide says an Arc is much better and GTX1650 is actually not recommended which has the same NVENC engine as the T400. What is the reason? The alternative would be the newer nvidia A400 but the hardware guide seem to focus entirely on Intel GPUs.

Where do you see that the GTX1650 is not recommended?  It is a perfectly good GPU for encoding.  Having said that, if I were buying a GPU specifically for encoding, I'd get the Arc GPU.  It is cheap, Intel Quick Sync is the gold standard for hardware accelerated encoding, and they support AV1 encoding.

Therefore according to the hardware guide the only option left is the "Sparkle Arc A310 ECO", which is the only single slot Intel Arc GPU I assume? But that seem to have firmware issues with its FAN curves, essentially it is switching only between 0% and 100%.

Or is there any other single slot GPU I'm overseeing.

The fan curve might be an issue for gaming, but should be fine for encoding.  Much much lower power draw.  I can't speak from personal experience, but I haven't heard about issues with the Sparkle A310's fan curve.

What my planned system is:

jellyfin server on CentOS Stream inside a VM (with GPU passthrough), the host will be FreeBSD, the hypervisor bhyve.

......No.  Why this configuration?  We don't support CentOS, or any Redhat based distro.  Nor do we support FreeBSD.  We don't have any guides for this configuration due to the lack of support.

This configuration is asking for a hard time.