Under your shopify dashboard, navigate to "themes" under "online stores" which is under "Sales channels". Here, click on customize button for the current theme you are using. Navigate to the PDP, where you want to change the padding.

Now, in the theme editor, click on the app embeds icon in the sidebar, now, search for whatmore in the search field.

Under the sidebar, we have option to change horizontal & vertical padding for mobile & desktop users.

Change the padding to zero, if you want to remove it completely.

As you can see. there is no padding for the floating video.

Under your shopify dashboard, navigate to "themes" under "online stores" which is under "Sales channels". Here, click on customize button for the current theme you are using. Navigate to the page, where you want to change the padding of a section.

Click on the section, where you want to change the padding.

Customization side bar will appear, where, you should scroll down, and the horizontal & vertical padding option appears, change it to your desired value. enter zero if you want to remove the padding.

The padding is thus changed.