Will my VR activity be posted to Facebook without my permission?

No. If you log into your Oculus device with your Facebook account, you can choose what information about your VR activity you post to your Facebook profile or timeline, either by giving permission to post or by updating your privacy settings. If you are an existing user and you choose not to merge your Oculus account and Facebook account, you will not have access to Facebook-powered social features and you will not be able to post your VR activity to your Facebook profile or timeline.