@DuckBrained - I'm relatively new to Unraid but I've also been facing the same issue myself - I have a couple of m.2 drives in an array that I use for video editing over my network which access via 10GB network. On this I can comfortably saturate the network get 1GB/sec read/write. However when I access the shares through the VM I am constrained to 250MB/s reads.
Could you possibly walk me through what you did to resolve this? Apologies - I'm relative new so I'm still finding my way around.