Hello
Just as a short introduction, I am a Windows system engineer by day with deep experience in powershell and Windows system administration.
I've previously did some freelancer projects in the past with optimising file transfer speeds to copy 100's of GBs between servers.
Although your use case is not the same scale, I can still use the methods of optimising your transfer speeds using powershell.
The method is quite straight forward and I can provide you with instructions on using it if you chat with me.
Thank you