I recently built a JONSBO N1 case myself and I am very happy with it (size wise), but unless you are looking for the same low profile feel, I would recommend looking at some of the other models as it's a bit tricky to work with. You also need to be extra careful with SATA cables and try go either get angled ones, or try to gently bend them before sliding the frame back into the case, as you might break the HDD connector board (which is explicitly not covered by warranty).
Next, be super careful with the Intel Chipset your Motherboard has - from what I can see the C242 Chipset does not support a CPU with graphics so you might not be able to use it for encoding/decoding (unless you meant putting a dedicated GPU, which also needs to be low profile single slot).
I got the Asrock E3C246D2I with the C246 Chipset and can confirm I can see intel display adapter listed in lspci (Linux).
(I also got a CBL-SAST-0933 Supermicro OCuLink to SATA cable, which is a bit more flexible and has lower profile SATA plugs, but the board comes with a cable as well that can work.)
If you're interested in a GPU that can only DEcode AV1, I'm going with an NVIDIA RXT A2000 (Ampere version) with a low profile cooler from n3rdware, which might also work for you.
(I haven't gotten the cooler yet, so I can't personally give any assurances how well it works or not)
There is also a different cooler version for the RTX 2000 Ada (Ada Lovelace) GPU from n3rdware, if you want to have AV1 ENcode as well.
If you are looking for a more budget friendly option, there is the Sparkle Intel Arc A310 ECO, which offers AV1 Encode/Decode and is low profile out of the box, however I wanted something a bit more powerful and also noticed some bad reviews about the fan revving up + it being loud (even post bugfix from Sparkle).
Lastly, be careful with server/workstation motherboards, as they have some quirks you would not expect if you're not too familiar with them (like I was).