Question Optiplex HD/SSD recommendation

[phicom]

Hi everyone I think this is my first post.
I just bought an OptiPlex 7010 running i5 and windows 10 pro. It came with a 1Tb HDD. I don't need anything even close to that size. For my needs even 250 GB is probably overkill. However I am interested in installing the OS on an SSD and the data files on a separate drive and using the 1TBHDD for backup.
Two questions:

1. For my purposes is it correct to think that a small HDD rather than a second SSD is fine for data storage?
2. The smallest SSD that I can find that seems somewhat reliable is a Crucial MX500 250GB.If that is the case is my initial idea of separating files between 2 drives really kind of unnecesary?

Thanks for your help.

 

[13thmonkey]

120GB with updates and temp files and programs that won't install elsewhere is borderline too small. 250GB is the recommened minimum size really. Sandisk/Samsung 860 or better also very good

 

[USAFRet]

250GB or preferably 500GB SSD, and put everything on it.
The current 1TB for backups.