Respectfully; I disagree. At least; I disagree that ALL solar is not cost effective. I've got a self-installed system on my roof that will pay for itself in 5 years, yet has an expected life of 20. Even if the ROI estimates are off by 2x, the system will still be a net-profit over it's life.
I DO agree that mass-market solar companies do not produce as cost-effective a system as you can build yourself. The labor costs they charge (for job planning, install, and on-going support) eat into the profit margins of the homeowner. They also limit the system size that they will install (often to no more than 15% above current average need or the like). This limit makes it so that you can't easily install a system (through them) that is as profitable as it otherwise could be. They also use a "one size fits all" material list and a generic blueprint. This is easier for them to turn installs, but does not generally result in the best outcome for the home owner.
Sorry; not true. Not assuming the panels are not maxed out under cloud cover. Assuming your panels and setup can handle the energy full sun can provide, then any cloud cover will reduce the output of the system. Here, for example, is the relative monthly output of my system as we passed from Summer into Winter:
Nothing has changed in the system during that time; it's all weather-related.
Every city and building inspector is different, but generally you only have to have things to-code that are involved in the upgrade. In the case of solar, that's going to be the mounting surface (eg; your roof; but it you have the space, there's the option of putting them on their own mountings) and your power main. Plus anything you install, of course, must be to-code. The building codes for solar are actually rather generous and not hard to meet.
I can't say how solar and wind would compare; I never looked into installing wind. But unless you have near-constant winds that are high enough to spin a turbine, I doubt that wind would be as cost effective. As I understand it; wind turbines require constant wind, as well - gusts don't work as well. Again; I've not looked into it, so all that is guess and conjecture.