idk about geography. i never took it to gcse.
but i remember teachers saying only ever bullet point if you’re running out of time and literally can’t write full sentences.
i was also advised (right up until a level) to write a plan on the exam paper with bullet points of what you planned on writing, that way, if you run out of time and don’t finish, the examiner will see what you planned on writing.
however i never did this because i was strict with my timings and preferred my plan being on the question paper.
so what i’m saying is, overall idk, because i did gcse’s years ago and never did geography. but i wouldn’t advise bullet point answers especially not for higher marked questions.
my view is why risk it? you’ll probably have time to write full sentences (that’s why they give you however much time you have), so just stick to the proper structure and don’t take risks. that’s what i’d do anyway.