Microsoft-SPO-CSOM-Set-WebPartChromeType.ps1

$wpManager = $file.GetLimitedWebPartManager([Microsoft.SharePoint.Client.WebParts.PersonalizationScope]::Shared)  
$webparts = $wpManager.Webparts  
$clientContext.Load($webparts)  
$clientContext.ExecuteQuery()

if($webparts.Count -gt 0){  
  Write-Host "Looping through all webparts"  
  foreach($webpart in $webparts){  
    $clientContext.Load($webpart.WebPart.Properties)  
    $clientContext.ExecuteQuery()  
    $properties = $webpart.WebPart.Properties.FieldValues     
    Write-Host "Title: " $properties["Title"]
    Write-Host "Chrome: " $properties["ChromeType"]
    $webpart.WebPart.Properties["ChromeType"] = 2 # 0 title and boarder, 1 title, 2 none
    $webpart.SaveWebPartChanges()
}