NAS upgrade time – UGreen or Sonology?

I’m finally hitting the wall with my aging Western Digital MyCloud NAS device. I’m just about out of space, so it’s time to look for new NAS options. UGreen and Sonology seem to be the current champions. To help me decide, let me layout my relatively meager use cases:

• This storage is mostly going to drive my Plex Server, which is running on a headless Windows machine on my local network. I don’t necessarily need (or prefer) to host Plex on the NAS itself. I know modern NAS devices are more powerful, but I tried this with my current Western Digital MyCloud device a few years ago and was spectacularly underwhelmed at its performance.
• I don’t typically bother with local backups of my phone, PCs, OneDrive, Google Drive, or iCloud. I used to do this with the MyCloud device, but over the years those services were all eventually deprecated by Western Digital, so I kind of got out of the habit. I’m pretty happy with the real-time online backup offered by the services themselves and have never needed something that wasn’t accessible, but if new NAS could do this quietly and effortlessly, I’d guess I’d be interested.
• I’m probably going to start with 12-16 TB of storage. Ideally, I’d want something that I could expand with more storage as I need it, but I can’t imagine when I’d need more. I don’t necessarily want to have to buy storage from the same vendor as the NAS device itself.
• And of course, I’d like to keep the cost as low as possible.

I’d appreciate any suggestions. Thanks!