Are there any specific RACF rules that would limit any of our current functionality with CA Librarian V4.4?
Look at your RACF rules you have set for the Librarian Master file.
The RACF rules you have set for the Master file under Librarian V4.3 will not change under Librarian V4.4.
The external security is set on the master file. It is not based on the version.
Please refer to the CA Librarian Security Administration Guide - Chapter 8 Using RACF