チェックアウト画面の代引きの表示が小さく分かりづらいので、CSSで文字を大きくしたりは可能ですか？
Unless you are on Shopify plus plan, you don’t have much control of checkout page, only what Shopify offers and i believe changing font sizes is not one of them.
You can still go to checkout from customizer and try to edit and see if that option is there or navigate to checkout edit from settings.
Best