Need to upgrade mainly because the MyCloud is too slow (uses standard spinning disks rather than SSD). Speed, RAID1, ability to use SSDs and ease of use are the most important in order of importance (speed being most important). Thank you for your suggestions.
If you're looking for a replacement for your WD MyCloud EX4 that is faster and has the ability to use SSDs, the Synology DS920+ and DS923+ are both good options to consider.
The Synology DS920+ is a 4-bay NAS device with an Intel Celeron J4125 quad-core processor and 4GB of DDR4 memory (expandable to 8GB). It has support for RAID 1 and can use SSDs for faster performance. It also has a user-friendly operating system with a range of multimedia-focused features for managing and streaming media.
The Synology DS923+ is a similar 4-bay NAS device, but it has a slightly more powerful Ryzen (no media chip) processor. It also has support for RAID 1 and can use SSDs for faster performance, but it has an additional feature that allows you to use NVMe SSDs as storage space for even faster performance.
In terms of ease of use, both Synology NAS devices have user-friendly operating systems with intuitive interfaces. It may be helpful to read reviews and compare the features and price points of these NAS devices to find the one that best meets your needs.