Teams and sharepoint for project collaboration

There isn't really a "one size fits all" answer and one that I can address in this forum, but here is a way to think about it. Content that needs to be viewed by a broad audience is best shared in a communication site. Content doesn't often need to be edited by a broad audience but if it does, it could be stored in a specific document library on a communication site or team site depending on the use case. Cross functional team collaboration could be in a Team for shared projects but if the scenario is persistent collaboration between two departments, for example, a shared channel in Teams could be the best option. My recommendation is that you think about the scenarios and then come up with recommended approaches for each scenario. Consider the state of the content (draft or final) as well as the audience (limited or open to a broad group) and how long the content needs to be shared. Hopefully, that will help you frame the use cases so that you can have some consistent approaches within your organization.