Difference between workflow developer and workflow administrator

Hi experts,

Could you please help me to clarify the below doubts,

1 -> What is the difference between workflow administrator and developer OR Workflow developer has to take the administration responsibility. Im                  thinking two guys performs these 2 different roles. If it is correct, please explain me the roles and responsibility of them. 

2 -> What are the necessary customizations need to be done before starting the workflow modelling. I came across few threads in SCN, everyone                  talking about SWU3 only. But i found some more customizations need to be in SE16, SMQS, SWE2, SMLG, SM59. Please explain me what are            the customizations need to take before starting.  

Thanks in advance.