The second tells me nothing - how is this intended to be used? What scope is it intended to be used in? Why was it created? Where does it fit in the program flow?
In other words, my thesis is that if you aren't familiar with State, both State s and State fooAppStateType are fairly opaque.
In any case, most of the time one works with a specialized instance, for instance, one might have something likr
newtype AppState a =
AppState {
runAppState ::
ReaderT Config
(StateT AppState IO)
a
}
If you're trying to understand how a library works when you're not very fluent in the language, that's what the documentation is there for! Any good library (and this is an area where's lots of room for improvement) should document the types it uses and the idioms that it lends itself to, and as one accrues experience, the whole "learning to see common patterns" takes over. The great thing about a helpful compiler of the Rust/Haskell ilk is that you make fewer mistakes in between (modulo occasionally horrific error messages).
And I'm willing to vouch for this not being expert (ha) blindness - I have only recently become comfortable enough with these things to talk about them.