I have respect for some (former and active) Nxt devs (e.g. Come-from-Beyond and jl777), but I think they need to write better specifications. I have personally told this to jl777.
What you have above is very incomplete.
It is clearly incomplete. Outside developers mostly need the Nxt API documents, and they are easy to understand.
The next big feature is child chains. There is no specification for that, but the developers seem to be able to produce working code without specifications.