We are renting a car in Chiusi Italy for a week so we can drive around the hills of Tuscany. I see that the CDW insurance and Third Party Liability is included but is it necessary to add the Personal Accident Insurance and Windscreen Damage Waiver also?
No, I wouldn't. However, the better question is do you want no deductible? The deductible for damage is often 1500 Euro and can be covered by an additional fee for special insurance to the car rental company, by insurance offered by a decent broker such as AutoEurope, or by being reimbursed by charging the rental on certain credit cards.
What ever you choose or not, inspect the car and take photos of the entire car on pick-up and drop-off to avoid a surprise damage claim.
And if you do take photos of any damage upon pick up, point it out there and then.
I picked up a car at Fiumicino once. On the paperwork the lot attendant filled in a couple of small areas of damage. The whole car was covered in pings and scratches, including the roof. I kindly asked him to mark his diagram to reflect all the damage.