Yes. The documents you create are exclusively your property. You can save them online on OneDrive, or locally on your Windows PC or Mac.
Even if your subscription is cancelled or expires, you will still have access to all your files and will be able to continue downloading them by signing in to OneDrive directly with the Microsoft account you used to set up Microsoft 365. But you'll lose the extra storage that comes with your subscription, so if your OneDrive account exceeds your free storage quota, you'll need to save your files elsewhere or buy more OneDrive storage.