Is there a max limit on the number of projects/users/configurations?

The short answer is: no.

No limit on Users

There is no technical cap on the number of users using the system. The usage is limited based on what combination of licenses you have opted for.

No limit on Projects

There is no limit on the number of projects you can manage in the Aligned products.

No limit on Configurations

There is no limit on the number of configurations used on your system. This means you can set up several Aligned configurations in parallell, optimized for dedicated scenarios/end-customers/product lines etc.