Write speed with Unraid depends mostly on the hardware used, also if you just want to use the array or can use pools.
For the array, and using turbo write, if there are no controller or other bottlenecks write speed will be limited by the slowest disk in the array in that zone, e.g., with fast empty disks write speed will be around 200/250MB/s.
For pools, using a multi device SSD pool or a fast NVMe device/pool I get around 1GB/s with 10GbE.