When making a horizontal form, keep in mind you have to make space for the button.
In the Form, under 'Edit Form Fields', each field has it's own personal setting. One of the Settings is 'Responsive Columns Override'. This allows you to set column size (ex: col-lg-3).
IMPORTANT!!! Please remember to check the form on tablet and mobile to make sure you used the correct column size.
To change the column for the Submit button, you must go under Form Settings (the first popup where you can change name and email recipients). Halfway down is a setting called 'Submit Columns Override'. This allows you to set column size for the button only (ex: col-lg-3).