Hey @imramugh,
The featured images display in the archive or blog index whether it is the standard layout or masonry, it is displayed using the theme’s built-in image size. If you want to change it to something square, you might want to check out this old threads:
A custom code is needed so that a different size for the archive/blog index will be display while retaining the theme’s built-in image dimension will still get displayed in single posts. Perhaps, in addition to the code in the older thread, you would have to add this:
IF NOT Singular page Then
$thumb = will just be Medium
EndIF
Be advised that custom PHP coding is beyond the scope of our support under our Support Policy. If you are unfamiliar with code and resolving potential conflicts, you may select our One service for further assistance.
When adding custom codes, you will have to maintain any custom coding to make sure that it will still work after any updates or does not create any issues or incompatibility in the future.
Best Regards.