In case you are rebuilding your NUC in another case, I would consider expanding 8 GB to 16 or 32 GB, because very probably your library is very large. Besides RAM memory is not expensive nowadays, better be on the safe side with RAM. See also the next link: Best hardware for Core for large library
You had not mentioned your OS. Windows 10 needs unspecified additional space for upgrade etc. Now you write that you use Roon ROCK and taking into account that you use a 2 TB M2 SSD, you probably can leave far less than 25 % free space, but having only 1 % free space (or 20 GB) as free space may cause problems in case you will accidentally and unwanted copy several albums to the disk that is nearly full.
I don’t know if you use DSP upsamplingc: upsampling to DSD 512 is very processor intensive. My NUC in Akasa housing remains below 45 degrees Celsius when I upsample up to DSD 128. Above the housing gets lukewarm (DSD 256) or rather warm (DSD 512).