When setting up Uniform Cluster; should the uniform cluster connect to an external MQ Full Repos Queue Manager which is already setup and serving other cluster queue manager or build a 5 node Uniform cluster and keep 3 as Data Processing Queue Manager and 2 as Full Repos?

Any implementations teams have done and best practices. 

Hi Om

Speaking from the 'theory' side, unless converting a cluster which is essentially 'uniform' already, I would strongly suggest using the 'autocluster' mechanism to define your UC.  https://www.ibm.com/docs/en/ibm-mq/9.3?topic=cluster-creating-new-uniform

In a uniform cluster it is important that all members be identically configured, and using the shared ini and mqsc approach means there is much less scope for error.  Uniform Clusters are typically relatively small, so the 'management' load on FRs is minimal - in your example, I would include all 5 nodes in the 'worker' set.   Make sure when creating the CCDT(s) which you provide to applications that all nodes are included as well, to ensure even client balancing is possible.

Cheers,
Anthony