It all depends on what you’re trying to accomplish. Do you want a solution that brings up a modal box? Do you want a solution that covers the entirety of the page? Do you want something with a massive animation? Something more lightweight? Do you want something whose features are tied into Foundry? It all comes down to what design you’re going for honestly. There’s not a wrong decision. Just have to pick what works best for you.
Yeah, there’s not been a need to update Focus in a while. No recent bug reports or problems.
Code-wise the Modal stack will be a little more lightweight as some of its code is already contained in the Control Center stack. I personally feel like Focus “feels” heavier with its large-scale animation, but that might be what you’re going for. It will be up to you.
No bug report needed. It isn’t a bug. Some stacks will need to “see” the page as it loads to be able to determine the space it has available to it to work within. Sliders and tabbed content and the like often fall into this category of stack. Since the content is hidden away in a modal, the stack believes it has zero space to work within and those sizes itself accordingly, with a 0px height.