On sale is this 2 Bay NAS featuring an Intel Celeron J3355 dual-core CPU, 2GB RAM (Upgradeable to 6GB), Dual Gigabit ethernet ports and 2 USB 3.0 ports on the rear.
The NAS is suitable for Plex Transcoding, file storage, backups, Docker and more with support for RAID, JBOD, Single and SSD cache. The TOS operating system receives frequent updates, bug fixes and community requested features. You can even (unofficially) install other operating systems like Synology DSM.
I'd go for a 4-bay for not too much more.
2-bay is too limiting unless you have a specific use for it