Can you use Sidecar with 5G only to connect Macbook Pro to iPad Pro M1 devices reliably for work
Sidecar uses a wired or direct wireless connection. When using wireless there is a restriction against creating a mobile hotspot, but this restriction would not apply to a wired Sidecar configuration.
https://support.apple.com/en-us/HT210380
https://support.apple.com/en-us/HT204023