I'm not able to follow what you're saying beyond the typical belief that macOS running on Apple silicon is going to be amazing.They can match 13" MBP with their 2 year old iPad SoC. They can easily beat 13" MBP by a specially designed passively cooled computer SoC. Imagine a 14" MBP, thinner than MBA due to passive cooling, faster than 13" MBP.
What would be the use of MBA?
They can do that but I don't see the point in creating two really similar computers which can be equally thin, equally fast. Right now Macbook Air uses low power chips, MBP13" uses higher power chips. Apple Silicon for both these designs might be similar in power efficiency. So in theory you could put the same kind of SoC into an Air or MBP13".I imagine there will be different tiers of A series chips when they start shipping them in Macs. The MBA will probably get basically the same chip they will be putting in the iPad Pro, with around the same power envelope and passive cooling. MBP will probably get more cores running at higher clock speeds and more graphics performance (I still haven't figured out if they are going to make much larger chips with Apple graphics or still pair their chips with AMD discrete graphics), but in a higher power envelope with active cooling. So to answer your question the MBA fills a lower price slot than the MBP - without having to pay for expensive Intel chips they may be able to lower the price of the MBA a bit more.
So we can cool A12Z, a 9W cpu in an iPad chassis, passively, but we can't cool it in a MBP chassis, which is much larger than an iPad?A13 consumes >6W at peak.
A12Z is likely 9W because it has 33% more processing cores and 100% more GPU.
A14Z is almost certainly higher than 9W.
You can't cool 9W passively in a notebook chassis. The Intel MacBook Air uses a 9W processor but throttles significantly under load.
The ARM MacBooks will likely be the same as today in terms of form factor. If you don't mind throttling, choose the Air. If you need more performance, you need active cooling found in the Pro.
So we can cool A12Z, a 9W cpu in an iPad chassis, passively, but we can't cool it in a MBP chassis, which is much larger than an iPad?
Btw, Macbook Air uses 7W chips, and they do throttle, but A series chips are much more efficient than Amber Lake.
So 40% drop when under sustained load, pretty much the same as with actively cooled MBA.Apple can't even cool the A12X in the iPad Pro chassis. Not sure why you think A12Z is being properly cooled. You should read up on peak vs. sustained performance. There's nearly 40% drop in performance in GFXBench over time described below.
The 2018 Apple iPad Pro (11-Inch) Review ... - AnandTech
The current model uses a 9W chip.
Intel Core i7-1060G7 Processor