If NAT (Network Address Translation) or PAT (Port Address Translation) is implemented between 2 XCOM servers will it have any negative impact on the transfer capability?
Networking internals such as routing and using NAT (Network Address Translation) or PAT (Port Address Translation) should have no impact on XCOM which is just operating at the TCP/IP layer of the network. Of course, after NAT or PAT is implemented, the required network and port connectivity will need to be in place between the 2 XCOM servers involved in the transfer process.
This information does not depend on XCOM release/version.