Google Drive. All G Suite apps store files there. A particular G Suite app's file list will only show files from your Google Drive that are editable/viewable by that particular app.
Google drive app if you just want to manage your data in the drive you have. Google docs if you wish to edit the file. Also google docs if you just want to work with doc files as google docs will list all previously edited files in the app.
Will we ask the question do I need Word if I have a file explorer?
I can never remember if my stuff is in Google Drive or Google Docs.