Depends how much data you have. I personally wouldn't use the network. It takes forever unless you have gigabit ethernet and it's a pain to set up! I have a couple of external 2.5" SATA disks and USB adapters. These are great for moving things around quickly. WD sell some cheap ones. They are quite robust. Something similar to:
https://www.amazon.es/dp/B00H53ET0C/
I would suggest migrating your files carefully to the correct folders (documents, pictures, video, music etc) in windows 10 on the C: drive rather than putting them on a separate disk or partition. This puts them in sub-folders of c:\users\yourusername along with all the bits of hidden profile information that is stored with applications etc. It also allows windows explorer to pick up all the metadata and integrated applications properly. This is an arduous process but it really does make the machine considerably more usable!
If you hose your machine entirely there's little benefit in having your data on a separate partition as there is no protection against the main failure modes: disk failure, infection, NTFS failure, corruption. I very much doubt you will ever have to reinstall the OS and if you do, you're then putting your files at risk of partitioning accident anyway.
Make sure you keep an entire backup offline and disconnected from the machine as well. One of the fun failure modes I've seen recently is power supply failure and it takes out the board and disks. The USB disk mentioned above will also serve as a backup device.