Does anyone know the difference between a project management module and suite projects?

Not totally sure what you're referring to by suite projects. Project management is the "real" projects (that you have to pay for on top of base Netsuite), with the ability to manage time, resources, rev rec, and such around project records. Basic project (which is free with base NetSuite) is essentially just sub-customers by a different name with a few extra fields added in. Projects SuiteApps, like the Project 360 Dashboard are additional things you can install in your account to provide additional pre-built stuff around projects (like dashboards, reports, etc.)

SuiteProjects adds resource allocation and forecasting features to the basic project capabilities.