In the US, we add the last name, but only when needed to distinguish the two. Grandma Smith is a vegetarian, but Grandma Chen isn’t. (Mom talking to her child about her two grandmothers)

Yes, they're the same in English. You can add maternal and paternal to specify which side you mean, but speakers tend not to differentiate between the two sets of grandparents unless it is necessary or unless it is genuinely hampering communication (Eg: my maternal grandparents live in city A, my paternal ones live in city B). Yes, it is confusing if you are a speaker of a language where the distinction IS made. If you are a translator like me, it is a nightmare because you can't tell in normal everyday conversation.

Yes, but if you want to differentiate, you can add “paternal” for you father’s parents and “maternal” for your mother’s parents. For example: “People say I look like my paternal grandfather.”

Sometimes though we use different names for grandparents to distinguish them apart. My son called my mom “Grandmother” but my husband’s mom “Nana”. He calls my dad “Granddad” but my husband’s dad “Grandpa”.

In English,it's same.❤️💛💚