Ok, so I built a new PC

[PeterBJ]

I agree. I have a computer with a USB 3 external HD attached. I can also attach a HD to an e-sata connection, and the e-sata disk is much faster. USB 3 is a vast improvement over USB 2 for external HDs, but the winner is e-sata IMO.

 

[mikling]

If the budget and space allows another HD, then put one inside the case. I hope you have a HD with an on/off switch.
Then use the following software or better if you have something better. Macrium Reflect Free, Crashplan and Create synchronicity.
Always make complete images of your 500GB SSD before any software additions or upgrades to either or both the internal or external HDs. Macrium has saved my butt and works well with Win10. Did I say it was free?
Use Crashplan to continually backup your data folder to the internal HD.
Use Create synchronicity to periodically backup either the entire data folder or the crashplan file offline.

If your budget even allows another SATA SSD as well, then the ideal way ( to me as others will have other considerations) is to use another SSD for working files and downloads etc call this the data SSD. Use Crashplan to backup this Data SSD to the internal HD. You will periodically move folders from the Data SSD to the internal HD to free up space on the Data SSD. The external HD is then used to backup the internal HD as well as store images of the system. Retain multiple images of the system over time. You will want one when Win10 was installed clean and updated with no apps and keep this one. The after the apps are installed, image again. Thereafter, you can rollover the images with apps. You will use create synchronity to backup the internal HD to the external HD. This budget SSD does not have to be large or fast ..just reliable, its size will depend on how much data you shuffle around. It does not have to be a super fast drive like your M.2 EVO. Even inexpensive drives will easily outrun the HD anyways, especially in reads. If you can still get an older MLC nand SSD, then that would be good since this drive will be subjected to a lot of writes. They say the new 3D nand from Samsung so consider getting a EVO SATA SSD. You will want to see what the write spec durability on this SSD is. In reality, I imagine any inexpensive will actually do the trick just stay away from the older 2281 controller ones for this application.