I assume the Qnap DAS you are talking about is this one :

https://www.amazon.co.uk/dp/B07K23ZJFN?psc=1&ref=ppx_yo2ov_dt_b_product_details

I was recently in the same place as you and i've bought this.. i have 2 x 16TB drives and 2 x 6TB drives in it all presented as individual drives.. i've spent the last week syncing my data to the drives and it's been faultless (this is a backup server for me)

I run Proxmox on a Lenovo USFF m910q and have passed the USB controller through to a windows VM running on it and file transfers max out the 1GB connection using rclone.