You can audit the placeholders using the Chrome extension. To look at the layout on the mobile site, you need to use chrome developer tools.
Right click + inspect a URL in Chrome > the developer tools open on the right typically.
At the top left corner of the dev-tools, there's a small icon that looks like a desktop with a mobile device inside of it.
Click that icon. It now allows you to select a device just above the content window (select the mobile device you're able to see the issues with on your actual mobile phone).
Refresh the page. You'll now see the mobile version of the site.
You can then activate the placeholders via the Ezoic chrome extension. From there, you can audit which placeholders are causing issues and take action.