List Shared files + File Size in ODB

 Pls check below script to get Sharing details of single user ODFB . and You need use PnP Sharepoint Online  Powershell module. 

$cred = Get-Credential
Connect-PnPOnline -Url "https://tenantname-my.sharepoint.com/personal/admin_tenantname_onmicrosoft_com" -Credentials $cred
$Ctx= Get-PnPContext
$lists= Get-PnPListItem -List "documents"
$Files = @()
foreach( $list in $lists)
{
    $FDetails = "" | Select "FilePath","SharedWith","FileSizeInMB"
    #Check weather is file or not
    If($list.FileSystemObjectType -ne "Folder")
    {
        $roles= $list.RoleAssignments
        $Ctx.load($roles)
        $Ctx.ExecuteQuery()
        #check file is shared 
        If($roles.Count -gt 0)
        {
          #Join Shared UserName 
          $rec = ''
          for ($i = $roles.Count -1; $i -ge 0 ; --$i)  
           {  
         
                        $m=$roles[$i].Member
                        $Ctx.Load($m)
                        $Ctx.ExecuteQuery()
                         If($rec) 
                         {
                          $rec=$rec + ";" + $m.Title
                         } 
                        Else
                         {
                          $rec=$m.Title
                         }


            }  
            $Ctx.ExecuteQuery()
            #Add File Informations
            $FDetails.FilePath=$list.FieldValues["FileRef"]
            $FDetails.SharedWith =$rec
            $FDetails.FileSizeInMB= $list.FieldValues["File_x0020_Size"]/1mb
            $Files +=$FDetails
            $FDetails =$null
          }

      }
  }
  $Files |fl

Note:

If you want to check each users ODFB sharing details, you need to add secondary site collection admin for each OFDB users, You can refer below link for add secondary admin to ODFB users

http://www.jijitechnologies.com/blogs/add-remove-secondary-site-collection-admin-to-all-onedrive-for-business-users