No specific region for hard exudate in DR. It can be found any place in the retina after BRB breakdown! bye the way exudates is much less in other vascular retinopathies than diabetic....like hypertensive, ROP, .....etc
Hard exudates usually appear around a source of leak, like microaneurysm/ hangioma/choroidal neovascular membrane. Actually, they are lipid deposits.
Soft exudates which are infarcts of the nerve fibre layer are usually seen around the optic disc or at the posterior pole as nerve fibre layer is thick there.