I’ve had synology, QNAP and a few DIY builds. I can tell you the diy route is better every time. They get a much longer life and lower costs.

If cheap is the most important thing and you don’t need more than 2 drives, consider an odroid HC-4. You can always 3D print a different shell for it if you want too. I made a cylinder Mac Pro shell for a friends dads build.

You can’t rely on mass produced NAS devices because they don’t support their stuff long term. It always blows up. And when the In go wrong in the short term, the support is trash tier. I once had a synology that would crash every time it went to sleep and it would ignore my attempts to sleep off. When I got hold of support, they told me to open the SSH port to the WAN for it and they would get to it in a week or 2. Damn thing was attacked instantly.

Never use an off the shelf NAS.