Sure, I'll share the part that relates specifically to s2Member. But it's really quite simple:
#s2member-pro-paypal-checkout-form-description-section,
#s2member-pro-stripe-checkout-form-description-section {
margin: 1em 0 !important;
font-weight: bold;
}
#s2member-pro-paypal-checkout-form-submission-section-title,
#s2member-pro-stripe-checkout-form-submission-section-title,
#s2member-pro-paypal-registration-form-submission-section-title,
#s2member-pro-stripe-registration-form-submission-section-title {
margin-top: 1em !important;
font-weight: bold;
}
#s2member-pro-paypal-checkout-form-first-name-div,
#s2member-pro-paypal-checkout-form-last-name-div,
#s2member-pro-paypal-checkout-form-email-div,
#s2member-pro-paypal-checkout-form-username-div,
#s2member-pro-stripe-checkout-form-first-name-div,
#s2member-pro-stripe-checkout-form-last-name-div,
#s2member-pro-stripe-checkout-form-email-div,
#s2member-pro-stripe-checkout-form-username-div,
#s2member-pro-stripe-checkout-form-state-div,
#s2member-pro-stripe-checkout-form-zip-div,
#s2member-pro-stripe-checkout-form-country-div,
#s2member-pro-paypal-registration-form-first-name-div,
#s2member-pro-paypal-registration-form-last-name-div,
#s2member-pro-paypal-registration-form-email-div,
#s2member-pro-paypal-registration-form-username-div,
#s2member-pro-stripe-registration-form-first-name-div,
#s2member-pro-stripe-registration-form-last-name-div,
#s2member-pro-stripe-registration-form-email-div,
#s2member-pro-stripe-registration-form-username-div,
#s2member-pro-stripe-registration-form-state-div,
#s2member-pro-stripe-registration-form-zip-div,
#s2member-pro-stripe-registration-form-country-div {
margin: 1em 0 !important;
}
#s2member-pro-paypal-checkout-form-registration-section-title,
#s2member-pro-paypal-checkout-form-custom-fields-section-title,
#s2member-pro-stripe-checkout-form-registration-section-title,
#s2member-pro-stripe-checkout-form-custom-fields-section-title,
#s2member-pro-stripe-checkout-form-options-section,
#s2member-pro-stripe-checkout-form-coupon-div,
#s2member-pro-stripe-checkout-form-billing-address-section-title {
display: none;
}
#s2member-pro-paypal-checkout-form-custom-reg-field-terms---conditions-label,
#s2member-pro-stripe-checkout-form-custom-reg-field-terms---conditions-label {
font-weight: bold;
}
#s2member-pro-paypal-checkout-form-password-strength,
#s2member-pro-stripe-checkout-form-password-strength,
#s2member-pro-paypal-registration-form-password-strength,
#s2member-pro-stripe-registration-form-password-strength {
margin-bottom: 1em !important;
}
#s2member-pro-paypal-checkout-form-billing-method-section-title,
#s2member-pro-stripe-checkout-form-billing-method-section-title {
margin-top: 1em;
}
#s2member-pro-stripe-checkout-submit {
margin-bottom: 2em;
}
.s2member-pro-stripe-form-card-token-button i {
display: none;
}
.s2member-pro-stripe-form-response-error,
.s2member-pro-paypal-form-response-error {
color: red;
}