When designing a Dell Unity XT 480 using the System Designer option of Sizer, the recommended minimum amount of Flash to specify is 15%. This ensures that there is sufficient flash capacity to handle performance-intensive workloads and provides a good balance between performance and cost. Flash storage is crucial for achieving high IOPS and low latency in the storage system. Reference:Dell Unity XT Sizing Guide

The maximum number of data drives that can be put in to a Dell PowerStore 1000T base enclosure is 21. The Dell PowerStore 1000T has a 2U form factor, and it supports a maximum of
21 drives in the base enclosure. The drives can be either SAS or NVMe, and it's important to keep in mind that the maximum capacity of the system depends on the type of drives that are used. It's important to note that the PowerStore 1000T supports up to 2 expansion shelves that can hold an additional 21 drives each, for a maximum of 63 drives in total. Also, the PowerStore
1000T supports up to 4 NVRAM modules that are used to cache metadata and improve performance.

https://www.delltechnologies.com/asset/en-us/products/storage/industry-market/h18149-dell-emc-powerstore-platform-introduction.pdf

The recommended maximum cable length for PowerStore back-end NVMe cabling to avoid performance issues is 10 meters. This recommendation helps to ensure signal integrity and optimal performance across the NVMe interface, which is critical for maintaining the high throughput and low latency characteristics of NVMe storage.