Help understanding FSE

Hi,

I currently have a couple of questions regarding the FSE Workflow. I normally write custom Themes using HTML, CSS, JS and PHP. You know the drill. But I wanted to see what this new cool way of doing themes is all about.

So I redesigned the website of my partner and set up a FSE File structure. Read some of documentation and got the hang of themes.json relatively quickly. It is a indeed a nice way of defining the design system.

However, I don't find any documentation on what settings I can change for the core blocks.
My IDE makes some suggestions when I type a character, but tbh. I don't want to guess.

Also it is kinda weird that for some Blocks I can add padding and margin, for others not.
I am currently trying to create the header and can't figure out how to add my CTA to the Hamburger Menu on Mobile Devices.

Also the ROW Block seems to be flexbox, but how tf do I align Items to baseline?

What part of the docs am I not finding?