I've been thinking a lot about this. Virtual desktops gets us somewhat close, but not quite. You're right the difference in resolution and colour depth isn't really relevant any more.

What I think made screens feel different was as a grouping mechanism, usually driven by a single application (though in more recent versions of AmigaOS you could open "public screens") that would manage the layout for that screen. You can do that with virtual desktops, but it takes some effort to simulate the behaviour.

I'm slowly iterating on something like that for my wm. I now snapshot the (by default tiling) layout and restore it, letting me "open" and "close" screens/virtual desktops, and re-open the applications on them, so instead of opening a single application that opens a screen, I will open a "project" and it will open a desktop and multiple applications on it whose windows will snap into place. I'm not happy with it yet, but it feels somewhat closer to me to how it felt to use Amiga screens.

It feels like the concept faded with the advent of large VRAM and fast fill rate graphics accelerators. I remember old X Window System workstations supporting multiple concurrent windows with different color depths and modes. The hardware would compose windows from memory during display scan-out, all to save VRAM.

It’s basically just an SD TV signal, the vertical height in lines doesn’t change, it largely just swaps if each line outputs 320 or 640 pixels during its assigned time period.

Having interlaced and non interlaced modes at once seems a bit funky though, but I assume it just forces everything into interlaced with the non interlaced mode sections having the same line sent on both fields?

In the context of the Amiga you didn’t need to change the signal frequency, the underlying video signal stayed the same.

For wider pixels, the hardware just drew each pixel for longer, and for taller pixels each pixel spanned more lines.

Pixels weren’t real in the CRT days :)

Analog monitors don't care about the dot clock. They draw lines, but you can put whatever signal you want in the lines so long as the dot clock doesn't exceed the available bandwidth. So horizontal resolution is effectively a range you can change at any time and the monitor won't even notice.

Vertical resolution is very much part of the spec, but even then CRTs will sync to hilariously out-of-spec signals that gain or lose lines per frame. Sanely-designed graphics hardware like the Amiga wouldn't do this, but the Atari 2600 wasn't sanely designed and had plenty of games that played fast and loose with NTSC. Atari graphics hardware only generated a single line of graphics and relied on H-Blank effects for literally everything else. Even the vertical retrace signal was controlled by the game. So it was very common to see badly programmed games send too many lines, and a different wrong number of lines each frame, which nobody noticed until people started writing 2600 emulators.

I don’t know much about Amiga, but from this article I recognize the Atari 8 bit / ANTIC DLI heritage at play!