Can I put the simple tab groups and settings icons somewhere other than the side so my screen window is full size

Would you be able to attach a screenshot of your current layout, and perhaps highlighting what you're trying to get rid of?

Maybe it's just a matter of switching tabs from vertical to horizontal, and then hiding the sidebar afterwards? (Ex.:)

If the question is about addons.mozilla.org/firefox/addon/simple-tab-groups/ addon, then you might need to check its settings.