a) if iOS contains full support for linux ABI
By "new Mac CPU architecture" I'm sure they meant Apple Silicon, currently meaning the ARM-based M1. Although there are now M1-based iPads, I'm sure they meant macOS, not iOS.
Regardless, neither macOS nor iOS has Linux kABI emulation, either on Intel or Apple Silicon. You have to use a VM of some type to run Linux binaries on a Mac.
b) if iOS on non x86 architecture includes emulator for x86 instruction set
iOS doesn't, but macOS does. It's called Rosetta II, and it's what allows old Intel Mac binaries to run on it.
c) if both work well enough to support as fragile process as netinstall is to work nicely.
I did once try to get the Windows Netinstall binary to run in a Parallels VM bridged to the network, but couldn't get it to work.
(This was back in the 7.1 beta series when it kept roaching my CRS328. Fortunately, rolling back without netinstall worked.
I don't recall if I tried netinstall64.exe under wine64 at the time, and I currently have no compelling reason to reset one of my devices just to try it out.