The CSS below can be added to your child theme's stylesheet (CSS file) or via a plugin like Reaktiv CSS Builder or Simple Custom CSS.
/* Attempt to fix extra spacing on registration checkout page */
#ee-single-page-checkout-dv p>br { display:none; }
div#ee-attendee_information-hidden-inputs { display:none; }
References:
https://eventespresso.com/topic/button-too-low-registration-form-and-discount-option-for-3-5-customers-add-on/
https://eventespresso.com/topic/huge-white-space-at-bottom-of-page-before-proceed-to-payment-options/
https://eventespresso.com/topic/white-space-on-registration-page/
Check out more tips for Event Espresso