Q1. Does every account (PayPal,Sendgrid,Heroku,AWS,Mailchimp) need to be in a company's name to make the company liable for anything that might go wrong, not the founders (to a reasonable degree of course)? For example - say someone hacked into my personal Mailchimp Account that I also use for the business, executes a phishing scam and a victim (and my firm's customer) sues. If the Mailchimp account is in my name can I personally get sued, even though I was acting on behalf of the company?
Q2. What makes an asset (such as a Mailchimp or Twitter account) belong to a corporation? Does it need to be in their name? Does it need to be mentioned in the documentation I submit when incorporating?
The typical IANAL disclaimer applies, regulations may also vary based on your location. If you need reliable advice, you should consult a lawyer.
Nonetheless, we can apply some common sense here. That's what's usually in the law too. I am assuming by "company" you refer to a distinguished legal entity.
Q1: In any case I would strongly recommend creating company accounts. Mixing up personal and business accounts is always a bad idea, exactly for the reasons you outlined. In the same way that you should not run your business from your personal bank account, you shouldn't consume external services in any way that gives raise to the question whether it's for personal or company use. This is not the only consideration you should take into account of course, in the long run it will also be a hassle to delegate tasks and responsibilities if these kinds of accounts are mixed up with your personal affairs.
Q2: Most likely you will not have to submit the assets at the time of incorporation - businesses tend to acquire most of their assets after incorporation. It's usually clear that an external service account belongs to the company if that's the adress and billing information you supply when signing up. Always use e-mail adresses from your company domain, and avoid using personal ones but use generalized adresses instead (e.g. firstname.lastname@example.org).