About number 1, I agree but also slightly disagree.
I mean, it would be great if you have a niche and you stick to it but it's also something limitating. It's better to have the freedom of writing about whatever we want at the moment without the fear of stepping outside that niche.
You have the freedom to write about anything...
But having a niche... Gives you focus especially if you already have a job. If you have time on your hands... Then fire away at any and everything