network attached storage

i was planning on builinding a nas and I had some questions: 1)is there any other options apart from freenas? (I can be able to access the data on the go) 2) What si limetech and what does it do? will it be helpfull for me? 3) I have 2 4tb wd red and 1 3tb, if i’m not wrong, limetech does a thing call unRaid which let me have a hard drive as a backup for the other 2 drives. can i use the 3 tb hard drive to back up the other 2 4tb hard drives?

this is my parts list:

Intel Pentium G4600 crucial 8gb DDR4 (can put 16gb if necesary) Corsair Series VS350 Gigabyte GA-H110M-S2H 2X wd red 4tb 1X wd red 3tb

Thanks in advance

@Johndias Have you tried a Google search for information on this topic? Here is one article that I found.