Yes, different types of multi-component compounds exist, based on the level of accuracy of the composition information: alternate, formulation, and mixture. A multi-component compound is distinct from a structure having multiple fragments within a structure field that has been registered as a single compound (without registering each fragment individually). An alternate is a multi-component compound without quantitative composition information. A formulation is a multi-component compound with exact quantitative composition information. A mixture is a multi-component compound with semi-quantitative composition information.
It is possible to register polymers as multi-component compounds. Polymers can be stored with its monomer units, that are created by stripping the "leaving groups" (configurable) from the monomers. More details can be found here.