Q1.6: What is cmaxpktsz good for?

cmaxpktsz corresponds to the parameter "maximum network packet size" which you can see through sp_configure. I recommend only updating this value through sp_configure. If some of your applications send or receive large amounts of data across the network, these applications can achieve significant performance improvement by using larger packet sizes. Two examples are large bulk copy operations and applications reading or writing large text or image values. Generally, you want to keep the value of default network packet size small for users performing short queries, and allow users who send or receive large volumes of data to request larger packet sizes by setting the maximum network packet size configuration variable.

caddnetmem corresponds to the parameter "additional netmem" which you can see through sp_configure. Again, I recommend only updating this value through sp_configure. "additional netmem" sets the maximum size of additional memory that can be used for network packets that are larger than SQL Server's default packet size. The default value for additional netmem is 0, which means that no extra space has been allocated for large packets. See the discussion below, under maximum network packet size, for information on setting this configuration variable. Memory allocated with additional netmem is added to the memory allocated by memory. It does not affect other SQL Server memory uses.

SQL Server guarantees that every user connection will be able to log in at the default packet size. If you increase maximum network packet size and additional netmem remains set to 0, clients cannot use packet sizes that are larger than the default size: all allocated network memory will be reserved for users at the default size. In this situation, users who request a large packet size when they log in receive a warning message telling them that their application will use the default size. To determine the value for additional netmem if your applications use larger packet sizes: