There is no rule of thumb when building modules in terms of number of dimensions or line items as each company's model will vary significantly. One great thing about Anaplan is that we are not limited on scale so you don't have to break larger modules into smaller ones, however there are a few reasons why you might want to. The design really depends on how the company wants to utilize the model. What is the module/model trying to accomplish, what do you need the end result to look like, who will access the modules, who will input into the modules, etc?? So, having said that, we typically set up 4 different types of modules:
1. Assumption modules,
2. Input modules,
3. Calculation modules, and
4. Reporting modules
Setting them up in these 4 categories allows for easy access for users to know which modules need their interaction for updates (assumption and input modules) and which modules create the results of the assumptions and calculations. Breaking the modules into smaller modules also allows a company the ability to limit the information an individual can see as they can set an individuals access only to applicable modules.