MARK !!! PASTE IT ON BOTTOM OF THE : theme.liquid
u can find it when u open your themes and click : edit code !
This code works by overriding the button you wanted to change with the “More payment options” button, and creates a super enigmatic button with the text “BUY NOW,” making it perfect for an online store.
Just to clarify: the shared code, above, is more than just the style you might be looking for. If it works (havnt tested), you should only copy the <style></style> contents. And probably put it into a CSS file - or the relevant liquid file - instead of just blindly in theme.liquid.
To answer your question more generally; yes you can update the “More payment options” text to look like a button, using CSS.
Generally though, I think it’s best practice to have it look tertiary to not “compete” with the actual CTA buttons.