1. I'm a power blogger, so I try to upload postings and pictures every day.
2. I'm a powerful blogger, so I try to upload postings and pictures every day.
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Q1: Can we use 'powerful' in place of 'power'?
Q2: What does 'postings' mean? Does 'postings' mean 'posted messages' or 'posted documents' or 'posted data'?
I guess you can use "power" and "powerful" interchangeably in this context, but "powerful" comes across strangely to me.
Each message added to a blog as a separate entry is considered a post or a posting, yes.
In this case, "power blogger" should almost be treated as a single term. Sometimes in American English, "power" is combined with a noun to indicate the person is very skilled or does the activity a lot. "Power user" is a common term in computer science to refer to a user that has advanced knowledge or needs access to a lot of advanced features.
For instance, most databases or search engines have a basic search function that most people use. Most databases also offer an "advanced" search feature. This advanced search box is more complicated, so many average users lack the skills to use it. Those that are skilled enough are sometimes called "power users."
Powerful does not really capture that meaning.
Q1: Yes, you can use "powerful" in place of "power" in the sentence. Both "power blogger" and "powerful blogger" convey the idea of being influential or having a strong impact as a blogger.
Q2: In the context of blogging, "postings" generally refers to the content that a blogger shares on their blog. It can include a variety of things such as written articles, photos, videos, or any other form of media that the blogger publishes on their blog. So, "postings" can be understood as the collection of all the content that is uploaded or shared by the blogger on a regular basis. It encompasses both "posted messages" and "posted documents" or any other type of content the blogger publishes.