Hi,
You won't have to redo your customizations. However, some of the options in the different views of the checkout workflow work work for you.
For example, we'll add a "show submit" yes/no option to the login view which will allow you to display the next/register button or not in the view without having to add any CSS. However, this option required us to add a bit of PHP in the view to handle it.
If you have an override in the sub_block_login_registration.php view file, then you won't get that bit of PHP in it and while the view will still work like before, the new "show submit" option won't work for you unless you redo that view override.
