I would like to ask another phase 4 question: how does auto-draft work?

After I buy a lot of mercs, the draft is usually up to 2B - every 6 minutes! - which is significantly more than my camps can produce. When I then go idle over night, I am currently very disappointed that I only got the armies from the camps but no single draft in the morning.

Would that be different with auto-draft? So could I empty all merc camps, go to sleep and when I come back I additionally have all the nice armies from the sliding drafts part?

And I assume I have to invest a lot of AP until I get to the 6 minutes schedule?

If you max out auto-draft to 0 (instant draft claim every 6 mins), then it's exactly that, you get every draft asap, and you empty the sliding pool quickly effortlessly. So if you'd get 2B drafts for ~20-25 drafts, you'll automatically have those armies when you wake up. It's one of the few Autos that is actually good. Safe to use, it can't hurt you. Also can't disable it, but there's no need to disable it, unlike all the other autos which you need to be careful with else you can destroy yourself quickly under the wrong conditions.

Maybe I should really stop maxing out IACP and start working on phase 4 instead :)

Once you've unlocked phase 4, you should stop investing ANYWHERE ELSE until you've maxed out Better Hospitals & Increased Army Caches.

Not exaggerating.

Only exception is maybe if you're doing Tech Runs trying to get Achievements (you might need to focus on Smelter/Crafter Speed, etc), trying to win WZIBs, beat the WZIC levels, etc. These may require Autos, etc.

But if you're trying to clear levels BH + IAC is the biggest benefit you can get.