Heh, mine’s not so different, multiple subnets - plus Wireguard :)
I don’t exactly know why but in the end it was definitely a inter-vlan connectivity problem I kept hitting. The pain was trying to prove it out as the official Nginx Proxy Manager container for unraid didn’t include anything like ping / traceroute etc.
I put a passively cooled GT1030 in mine and its doing the decoding & tensorrt detection for 4x 1080p cameras just fine, based on its current load I expect I could add another 4.
I couldn’t tell you if that specific Amcrest camera will work, but I have 2 of the recommended ones on the frigate docs (https://www.amazon.com/gp/product/B083G9KT4C/) and they work.