usb c 3.2 gen 2

Just purchased a new Samsung 4TB T9 SSD. I have it connected via USB-C into a 20gb port on my new PC. When I first started using it, I was able to transfer a 6GB movie file from my internal SSD onto the T9 in about 10 seconds. So after that I began to copy over a lot of my personal files. Then...

I have a 16T and a 10T drive and want to span them in Win 10 Pro using Disk Manager for (approx) 26T. They are both formatted as NTFS and the partition table is GPT. I go through the Win 10 Disk Management steps to span or stripe them and regardless of what I do I get a Virtual Disk Manager...