Hi Guarav, thank you!
For the content type, there's no universal rule, it's really just common sense.
If the article is a tutorial it falls under "how to", if it's a general, high level article about a topic, it can be categorized as "learn about [the topic]" or so.
To decide what type each piece is, you do first the content inventory, then look at all the content that you have and depending on your scope (all articles, only the high traffic ones, only those targeting a specific industry etc.), you start assigning them to a certain type.
Some articles might fit in more types, for example how to, or guide, or learn about, so it's up to you to decide how to split them and how many types to use.
The purpose of this process is to help you figure out what works for your particular client or business.
So if you notice for example that your case studies have high conversions, write more of those. If TOFU articles ('how to' for example) are generating lots of traffic but no conversion, decide whether you want to write more of those based on your general goals.
Regarding the stages of the funnel, there's the general ones - top, middle, bottom, but what content matches each stage varies again.
For example, there's a common belief that "awareness" or TOFU means that people are unaware of the problem and you need to educate them, thus you need to create a lot of high level content about the topic.
However if you're focused on conversions, awareness or TOFU most likely means that users are aware of the problem and just research potential solutions. So you don't need to educate them about the whole industry and product category, you only need to make them aware of your specific solution and why it's better than others.