I don't claim to be an expert, but the key questions for me is, ¿which environment do you feel more comfortable with?
* Java -> JBake. Easily installed with sdkman and uses asciidoctor as first class citizen, unlike others that use markdown. This means all styles should work perfectly.
* Ruby -> Jekyll or Middleman. It can all be installed using normal "gem" command, and you can use the versions with "bundler" to better control the versions you use. I've used it and the live preview features are really good. Just google and you will find some examples and templates ready to use.
* You don't care -> Hugo or any of the others. Hugo got a attraction for its OOTB lightness & speed, but in the case of asciidoctor, it just calls the asciidoctor gem in a separated process. So you don't get the full Hugo power and you still need to install Ruby and the required gems manually. The good thing is that there are many templates and styles to choose and since it uses the gems, you can use any extension and the latest asciidoctor version. A good point is that Hugo documentation is really good and even includes video tutorials. I did a proof-of-concept some time ago and I could meet all my requirements and publish on gitlab using "google driven development".
* You'd like to get something quickly without much hassle -> https://github.com/HubPress/hubpress.io. It's an (imho) under-appreciated online solution. I see however it hasn't received recent updates, you'll be missing a few new features, but nothing critical.
In terms of complexity, they are more or less the same. They provide some template to inject headers, footers, menus, etc. and require you to define some asciidoc attributes to build the site. They convert AsciiDoc sources using the "--embedded" option so the HTML can be inserted in a div as you mention, then it uses the style css provided by each tool.
Can't comment on "asciidoctor stylesheet factory", sorry.
> Should I use asciidoctor stylesheet factory to render the articles according to my theme?
I would recommend creating a new stylesheet for your site. You can use the one in https://github.com/asciidoctor/jekyll-asciidoc-quickstart as a starting point, or any of the other sites I mentioned. I don't recommend using the asciidoctor-stylesheet-factory as that is now only intended for use by Asciidoctor core to generate the default stylesheet. Otherwise, it's not maintained.