Is mining upgrades sometimes a downgrade?

The upgrade was to not use manpower at all.

Not sure but I think it’s intended to save manpower for convenience. One machine manned by someone with a high labor skill probably does produce goods at a faster rate, while an automated machine can produce at the same speed even with a level one recruit.

I make compact bases, so the automated upgrades such as an auto-fabric machine aren’t very useful to me, due to tying up a laborer anyway. However, if you have two auto-machines running at once, that same laborer is now producing twice as much goods as he runs back and forth between the machines.

So, someone with a big base and large production lines can make better use of them, but for smaller, more skilled forces, probably not so much.

If you upgrade your steel bar production it will literally vacuum up all your resources so that all your other production that needs iron plates comes to a halt. Steel bar upgrades simply gives you something like 2x speed 2x cost, instead of something useful like efficiency of material use. I usually build 2 iron plate producers for one level 1 steel bar producer and leave it like that, otherwise you can expect to never have the resources you expect.

If you’re using the 256 people mod then yeah, I generally agree. It saves manpower at the cost of resources, which matters if you want a larger settlement but are stuck using too many of your 30 guys just to keep the place running smoothly. If you don’t have that limit, and your PC can handle it, then yeah you’re better off just hiring a bunch of cheap people to train up in whatever skills. You can automate them in essentially the same way, only faster.

Or if for roleplaying reasons you don’t want to have a bunch of people, but want to have production.

You can use previous versions of the machines if you want.

Power should never be an issue.

Efficiency wise I think they are the same.

If you're crafting weapons and armor, your workers are probably just taking all of your steel and iron before it even gets to storage.