Here I did some benchmarking of different systems a while ago. Among the tested systems I had a Pi4 with 4GB RAM and a MiniPC with an Atom x5-Z8350 CPU and 2GB of RAM.
My benchmarks did not include any Video-related tasks, only stuff Home Assistant itself is doing. But it still might be helpful. In my tests the Pi4 and the MiniPC where pretty close to each other. But as the MiniPC you’re looking at has a faster CPU and more RAM, you should see the performance improve. Additionally the CPU in your MiniPC has more support for hardware accelerated Video-stuff. If the software you’re using is able to make use of that, then this should have an impact on the performance as well.
So my guess is, that your MiniPC will certainly be better than the Pi. But I can’t say if it’s powerful enough for your requirements, especially regarding the Video stuff.