Welcome. I am you except I've been doing servers ever since the early days of the commercial Internet.
Microstar is ... I don't even know what that is. Did you mean Supermicro? If so, I'm the guy who drove the mass exodus to Supermicro gear here about ten years ago. They're like legos for server geeks, you can build whatever you need.
Please consider going to have a full read-thru of my decade-old article:
Mod note: This thread is jgreco's original hardware recommendations guide, from back in the day. General advice still holds, but some specifics have changed. The current Hardware Recommendations Guide can be found in the Resources section, at the following link...
www.truenas.com
Which is still really relevant in many ways, but it's really aimed a bit more at techies who have SOME experience with computers. I think this would be helpful to you.
Dell prebuilts certainly work, but Dell's systems like that R730 are dual socket affairs and probably not appropriate for basic NAS use. That one also targets 2.5" drives, which is limiting with ZFS where you shouldn't use SMR hard drives -- most 2.5" HDD's larger than 1TB are SMR. You can make a basic NAS out of a Supermicro rackmount chassis such as this:
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and then put in a middlin' old Xeon board like an X10SL7 and get a basic functional NAS platform. You can also get a larger board that is capable of more memory and more I/O, like an X10SRL, which can handle lots of memory. If you plan to do stuff like jails or VM's, then there are also dual CPU options that might make sense. So you can right-size your NAS very easily with the Supermicro stuff. And you don't even need to use a Supermicro mainboard in the Supermicro chassis, though there are advantages to doing so.