We plan to create quite a number of folder groups in USM, with some assigned to MCS profiles. Are there any constraints on the number of containers and folders that I should be concerned about?
There is no limitation in terms of number of containers and groups you can create in USM.
Please follow this documentation that will take you through the steps to create them:
Create and Manage Groups in USM - CA Unified Infrastructure Management - 8.4 - CA Technologies Documentation
Let us know if you have any questions. Also, you are welcome to open a support ticket should you have issues.