Depending on how old your business is, you might have several accounts. For example, one on Twitter, another on Instagram, and so on. Sometimes if you have several brands or products, you need to manage multiple accounts on the same platform. If you're a startup, you might only be thinking about your strategy and what channels you want to have.
In any case, before sitting down and planning your content, make sure that you understand what makes every channel unique. For example, Instagram and TikTok are very video-heavy and they mostly rely on short-form videos. Despite the growing popularity of Shorts, YouTube is the hub for long-form videos. Twitter and LinkedIn are more leaning towards text formats.
If you know what type of posts work on which channel, it'll be easier for you to plan.