If your company stores many files as attachments (Notes) in Dynamics 365, the storage costs will sooner or later become very expensive. You are not one of the first to come up with the idea of storing documents in SharePoint in a cheap and structured way.
Unfortunately, there is no one-size-fits-all answer to the question. The Dynamics 365 storage space is calculated based on the licenses and users. As a result, each Dynamics 365 environment has different storage capacities.
If you have budgeted enough for the storage costs, there are still other arguments for not saving the files as attachments. Information architecture plays a particularly important role. With Dynamics 365 attachments, there is no way to tag the files with metadata and search for them.