The 8i5 is still an excellent choice, if you are running multiple DBs and value good DB performance, get a Sabrent Rocket 4 1TB. If you want reliability at the expense of performance, Samsung 970 pro 1TB.
For SSD reliability with database use, never use more than half of its free space, if you need more space for file storage, make use of the SATA slot for an additional drive, Samsung 860 pro 2TB is the best choice there. For write once read many you can go to to 90% use, for constant write (like video surveillance) 80%. The 870 Evo 4TB gives you more space at a similar price but a lower life cycle and reliability rating.
If you need more than 4TB for file storage, you should not be using a NUC, you should use something with a RAID controller or a computer that can do mirrored drives
For RAM I suggest CT2K8G4SFRA266