If it's just a NAS, Gen8.
You won't be bothered by the RAM limitation and you can upgrade the CPU if required.
Thank you. I also have and idea, maybe to get a gen10 and replace my cyrrent desktop(i5,8gb ram). My current pc is mostly used to connect to RDP or sometimes im doing some programing with python. Maybe its posible to setup something like ESXi, to install windows, ubuntu and freeNAS, and connect directly to one of the vm's (not sure if it is possible)?