First, RAW 9 only runs on OS 27, so Intel Macs are out of luck.
Overall, RAW 9 looks great and I will definitely enable it. But, it has higher resource requirements, including memory. That means that some iOS / iPadOS devices may not be good candidates to use RAW 9. Since RAW 9 changes the appearance of images, that complicates matters further, especially when using iCloud or other synching between devices that can run RAW 9, and those that cannot (e.g., Intel Macs). You don’t want to be in a position where you edit an image on one device and it looks different when you open it on another device.