Assemblies and methods to enhance a fluid catalytic cracking (FCC) process associated with a refining operation, during the FCC process, may include supplying a hydrocarbon feedstock to first processing units associated with the refining operation. The assemblies and methods also may include conditioning a hydrocarbon feedstock and unit material samples, and analyzing the samples via one or more spectroscopic analyzers. The assemblies and methods further may include prescriptively controlling, via one or more FCC process controllers, based at least in part on the hydrocarbon feedstock properties and the unit material properties, the FCC processing assembly, so that the prescriptively controlling results in causing the FCC process to produce intermediate materials, the unit materials, and/or the downstream materials having properties within selected ranges of target properties, thereby to cause the FCC process to achieve material outputs that more accurately and responsively converge on one or more of the target properties.