I can point out the difference between LTE and 5G NSA (ENDC registration) based on my experience:
Basically Attach flow remains the same as LTE except for some additions as follows:
- If the cell of any network supports 5G, it will be indicated in SIB2 with "upperlayerindication for r15" as TRUE before Attach Request is sent by the UE
- In the Attach Request message, the UE will indicate that it supports DCNR in MS Network Capability with the bit value as "1" (I have seen this may not be true for all UEs) and additional security capabilities
- There will be additional messages for UECapability enquiry from the network to check the NR bands that the UE can support
- In the Attach Accept apn_ambr_incl will be set to "1" and the values for data rates can be seen.
The above is as per my knowledge. Kindly correct me if I have missed something or have shared the wrong information