Honestly, in my experience you could do everything with rows because you can override the default flex settings (for that matter you could do nearly everything with just f7-blocks too). But I think that using the alternating rows and cols if you’re actually building a grid of component is just slightly cleaner and easier code to read.
I do all my widget development in the MainUI editor. Nothing else that I’m aware of at the moment is going to give you the autocomplete ([ctrl] + [space]) feature that the editor gives you and it’s the only way to get the immediate preview.
My reference hierarchy is as follows: My first go-to is the autocomplete in the editor itself to see what’s available for a given component. If it’s not immediately clear what a particular property does then I’ll hop over to the the f7 vue docs to get the details. If it’s an oh- component, then it also helps sometimes to have a look at the autogenerated oh component docs but more often, I’ll check out the vue files on the webUI repository itself.