We have the Chicco Keyfit 30 and it comes with a newborn head insert/cushion. That's all we ever used for DS and never had a problem. I've also seen plenty of moms suggest using rolled up receiving blankets. I don't think you need anything fancy.
In general, you shouldn't add anything to your carseat that didn't already come with it, particularly things that would go under the baby. It can make the carseat less safe in the event of a car accident and may void the warranty. Our carseat has a basic infant support that came with it and DS was fine with that. As long as you have the carseat installed at the correct recline angle, the baby should be fine.
In general, you shouldn't add anything to your carseat that didn't already come with it, particularly things that would go under the baby. It can make the carseat less safe in the event of a car accident and may void the warranty. Our carseat has a basic infant support that came with it and DS was fine with that. As long as you have the carseat installed at the correct recline angle, the baby should be fine.
Re: Baby neck support
Yup! Agree