The visit report should be created after the visit to a customer to make sure you capture relevant information to be shared within the group. Or send the meeting minutes to the customer.

ALL objects as activities are related to all objects in salesforce.

The visit report must be created from the contact, thus bringing the information on account to the report.

Yes, it’s possible to log a visit report without logging a visit. Just click directly on New Visit Report from the Contact page. However, it is strongly recommended to log your visits in Salesforce (directly or through Cirrus) to keep track of them