What do you think makes a better NAS, a Raspberry or an Orange Pi ?
For tinkering about - Raspberry Pi is still a good choice, however, supply chains are definitely a challenge in this post-pandemic situation we find ourselves in - Pi4 is pretty good, and CM4 with a trusted carrier board could be an option.
For other Chinese SBC's - I prefer FriendlyElec, aka FriendlyARM - I've met them personally, and they put out a good product compared to others in this space.
I have a lot of concern on Orange PI - Shenzen Xunlong has a rep for spitting out boards that are not fully baked, and trusting the community to sort things out as they move on to their next experiment, i'm not saying they are bad or good, it's just others are better perhaps...
For a base software platform - can't go wrong with
Armbian on supported boards - I'll disclose up front that I do participate over there as a contributor, but it's a good team to work with, and they very much care for the community...
As I posted earlier - better to go with a known NAS vendor - QNAP, Synology, Asustor are all good - they do good product, support it if things go wrong...
DIY for NAS - it really comes down to risk tolerance - how much is your data worth?