Image manipulation natively supported by EE5 and Bloqs plugin. Using simple grid, the variables for the file field type nor image manipulations are not working.
Documentation from EE for Image Manipulation: https://docs.expressionengine.com/latest/fieldtypes/file.html#single-variable-usage
Documentation from EE for File field variables: https://docs.expressionengine.com/latest/fieldtypes/file.html#template-tags
In my example, image manipulation name is square. Files are already generated successfully. Directly creating a field in channel or bloqs are working. Only when it is within Simple Grid field type, it is not working.

{people_bloq}
    <div data-block-name="people_bloq">
        {people_entries}
            <div class="pb-2 text-center">
                <!-- Test: Simple entry (WORKING) -->
                <img src ="{people_entries_image}" alt="Picture of {people_entries_name}" class="img-thumbnail">
                <!-- Test: To get square version (NOT WORKING) -->
                <img src ="{people_entries_image:square}" alt="Picture of {people_entries_name}" class="img-thumbnail">
                <!-- Test: To construct path of the image using the built in variables (NOT WORKING) -->
                {people_entries_image}
                    <img src ="{path}_square/{file_name}" alt="Picture of {people_entries_name}" class="img-thumbnail">
                {/people_entries_image}
            </div>
        {/people_entries}
    {close:people_bloq}
    </div>
    {/close:people_bloq}
{/people_bloq}