The most important thing to know about marketing plans is that the author is almost always the only one that reads it... or at least all of it.

If you want to create something people will use, this is the structure of a concise deck format I've used for B2B with success. I've called it "Total Brand Awareness for Sales & Marketing." Structured like this...

1. Purpose - who it's for and what it is

2. Branding: Value Proposition: what you do for companies

3. Branding: Brand Promise: what you do for your customers

4. Product Brief: 1 paragraph descriptions of each product

5. Product Detail: product-specific value propositions, features, how it aligns with brand value proposition, the one most important buyer persona, and talking points for sales discovery calls

6. Buyer personas: 1 slide for each persona, bullet points for their goals, challenges, objections, purchase triggers, and your positioning for that persona

7. Style guide: how you look and how you talk

8. Social campaigns: what you're going to do on social media

9. Content marketing strategies: a concise 1-slide plan of the amount and kind of content

10. Paid media strategies: a concise 1-slide plan of keywords/sites/ABM points

11. Sales & marketing library: links to all supporting documents

People READ this and refer to it often.

I always make a presentation and then add a document with extended plans for further reading etc.

I do this for pretty much any big presentation/project.