Does GDPR apply to my startup if I'm outside the EU?
Yes, if you offer your product to people in the EU or monitor their behaviour (Article 3). Being small does not exempt you, though some record-keeping duties are lighter under 250 employees.
Do I need a cookie banner?
Only if you use cookies or similar tracking that is not strictly necessary, such as most analytics and all ad pixels. Cookieless analytics and a sign-in cookie alone do not need one.
Do I need a data protection officer?
Usually not for a small SaaS, unless your core activity is large-scale monitoring of people or handling special categories of data such as health. In Germany the threshold also depends on how many people regularly process personal data.
What is an Impressum?
A legal notice German law requires on commercial websites (§5 DDG): who runs the site, a postal address and a fast way to make contact. Austria and Switzerland have similar rules.