hi all, i'm new on this forum and sorry for my english, hope its fine!
I'm about to buy a NUC7I3BNH, and i know there is a M.2 ssd slot and a second sata.
Can i use my evo ssd (non m.2) to install windows 10, not using the m.2 slot?
Yes you can. The Windows 10 can be installed on your 2.5" SATA SSD. You can use your NUC with M.2 slot empty.
However I suggest to you to buy M.2 SSD 250GB (for example this one: https://www.amazon.com/Samsung-970-EVO-250GB-MZ-V7E250BW/dp/B07BN5FJZQ https://www.amazon.com/Samsung-970-EVO-250GB-MZ-V7E250BW/dp/B07BN5FJZQ ) and use this drive as a System+Program drive. The access to storage drive is usually a bottleneck in computers. SATA SSD has write/read speed about 520 MB/s when Samsung 970 EVO has writing speed of 3500 MB/s and read 2500 MB/s.
So, the performance of you NUC will be much better, using M.2 NVMe drive for Windows and other programs, while the 2.5" SATA will be used for data storage (pictures, movies, documents,...).