[mattbrewsbytes]

For a hobby project, solo developer to start means it is a personal choice. If you pick a stack that is new to you, carve out time to learn.

Don't bother considering popularity. If you are familiar with PHP and Python, see what frameworks for those are the best choice. For Python or PHP I have heard Django and Laravel are good frameworks, no experience with them personally. Model-View-Controller is a de-facto pattern with web frameworks and usually the framework will dictate file locations, structure of code, etc.

You mention data aggregator and users connecting data sources - that sounds like where the most technical work could be in your app. If this is consuming API's then that is pretty straightforward but if you get into screen-scraping or handling multiple ways to aggregate content then the available libraries/tools in your language of choice might influence your decision. I'd look into how you want to aggregate data first, see what tools are out there to help you.

Most web frameworks will out-of-box meet nearly all of your requirements. I'd be wary of code generation from a design tool. I'm not in the "must hand code everything" camp - it will work for an initial app but after you start adding features and changing things in your code the design tool that generates code won't match.

If you're up for learning something new, I would advocate for Rails. Once installed (along with DB) it has generators which can "scaffold" the parts of the app. I would guess PHP/Python frameworks have similar things. Google around for tutorials on this and try them out.