OneDrive is a person's own drive — it leaves when they leave. SharePoint is the company's drive — it stays. Teams is a conversation surface that stores its files in a SharePoint site behind the scenes. Every small business that stores company files in personal OneDrive folders eventually loses a project when someone resigns.
Design the structure before you migrate anything: a small number of sites that match how the business actually works (Operations, Finance, Projects, Clients), each with a few libraries, and permissions granted through security groups rather than to individuals. Broken inheritance on individual folders is the fastest way to an unmaintainable permission mess.
Sharing settings matter more than folder structure. Decide whether 'Anyone with the link' is allowed at all, set link expiry, and default new links to 'People in your organisation'. In a HIPAA (Health Insurance Portability and Accountability Act) or contract-heavy environment, external sharing should be per-site and deliberate.
The OneDrive sync client with Known Folder Move puts Desktop, Documents and Pictures into the cloud automatically — a cheap, effective baseline against ransomware and dead laptops. Files On-Demand keeps disks from filling. Watch out for very long paths and files locked open by another app; those cause the sync errors you will actually get paged about.