So as per your updated question and requirement of lightning component to view/load/download any kind of file in browser then you should get respective Content Version of the file you wish to view/download and form a URL.
If it is coming from an sobject record then get the contentDocumentId from the contentDocumentLink record whose linkedEntityId will be recordID. After you get ContentDocumentID, get the latest ContentVersion or number of versions as per requirement and form the URL like this
https://yourDomain.lightning.force.com/sfc/servlet.shepherd/version/download/ContentVersionId
If you want the file to be executed/viewed in browser go to File Upload and Download Security and choose that particular type of file and set the behavior.
UPDATE-- You cannot use a URL of
name-space.visualforce.com
in a lightning component. If you wish to preview/download a file uploaded in documents(classic), get that file in lightning either by uploading it manually(if single file or 2) in files tab or a customised code to convert attachment to contentDocument and Version and then get it's ID to use in Lightning component
You can only form the URL i mentioned
https://yourDomain.lightning.force.com/sfc/servlet.shepherd/version/download/ContentVersionId
which has lightning.force.com in your lightning component along with Content version id to preview/view/download following the above procedure.