Is there some documentation for what the combinators do in each mode, specifically what each input and output does on each setting?

Currently the mod information page - while extensive - reads more like a brochure/guide touting the mods capabilities, rather than documenting each piece. And there's no tutorial or other information out there from a google search, and no wiki on the github.

For instance, it mentions that there is a priority system - but not how to configure it.

It mentions that it 'Natively read out all deliveries currently in progress for a station, not just the loading or unloading orders of the parked train.
' but I don't know how to get that information, - and I also really need to know specifically what a particular train needs at a requestor stop wants, not what every train queued up at the stop needs.

Overall it looks like an interesting mod, but the information provided is not sufficient - and kinda comes off as a little too 'self congratulatory' for engineers who are interested in functionality.

Be careful not to confuse an enthusiastic (and accurate) description of features for pridefulness or self-congratulation. The mod author has put a lot of effort into this and has been very amenable to fixing bugs and considering new features, and has been quite humble in the interactions I've seen. It's also very stable and feature-rich for such a new and ambitious mod.

The priority system is dirt simple: use the priority signal that the mod provides and set a numerical value on it (you place it in the same constant combinator you would connect to the station control to set requests etc). Higher numbers are higher priority. Not much else to say.

The more advanced features could use some more detailed step-by-step guides or descriptions in some places, I agree; the mod author is self-admittedly not always the best with describing functions, although I do think I saw her mention somewhere that there were one or two things she wanted to encourage folks to explore on their own.

With how new the mod is, I wouldn't expect much in the way of a guide or wiki yet in any case. But if you're talking about functionality, getting started with the mod is overall not very complex. I had a much easier time getting a basic setup to serve my needs than I did with LTN, for one thing. Follow the quick start guide, then experiment with plugging inputs and outputs into things to see what they do.

Agree to disagree about the accuracy/pridefulness. The information brochure basically goes out of its way to say this mod is better than LTN, and says stuff like "Intuitive and easy to learn, without sacrificing features." But currently I'm not finding it to be any more intuitive. It may be easier to use the most simple option, but scratch the paint and LTN is easier to grok, especially due to its better tutorials & the existence of add-on mods.

In particular, I wish this mod would give a display for how its figuring out my stations automagically, and let me use the default LTN behaviour of defining my own station limits instead if I want to.

Compared to https://mods.factorio.com/mod/RailLogisticsDispatcher - which is probably what I'm going to switch to, especially based on your reply - now that mod is also very similar LTN, but with a GUI and information displayed that actually does make it easier to use.

There isn't too much I can do about the lack of thorough tutorials available on account of the mod being so new. I could make them on my own, and indeed I plan to write more in depth, in game documentation in a future version, but I am a busy person. If you don't find the mod intuitive, that's fair, I've tried my best to use UX design principles to make docs or tutorials not strictly necessary for people to learn the mod, but there are still aspects of the complexity curve I am unhappy with, and even the best UX design isn't going to work for everyone. Having a way to visualize the automatic train blacklist is actually a great idea, it might be a long time till I implement it, but it's going on my list.

I would like to ask if you've read the Mod Details section of the mod description. This section is not as thorough as I would like since it has to fit within the mod portal's text limit, but it does have most of the answers you haven't been able to find.

As for the whole accuracy/pridefulness thing, the Features section of this mod was intentionally written as a sales pitch for the mod to people already familiar with LTN, so I think that is where you are getting pridefulness vibes. This mod unfortunately will never be able to stand on just its own merits. LTN has years of head start and was created by someone well established in the modding community. Almost no one is going to want to use both LTN and Project Cybersyn at the same time, so I've got to convince them why they should give Cybersyn a chance.