- To answer your second question first, there’s a community-created wiki that’s been around for a few years, but there’s hardly anything in it yet about edge and the new architecture. However, it is a good place to find the list of community written edge drivers that are available for public trial.
There’s quite a bit of official documentation, but all of it is still in development and some of it is contradictory. So you can definitely get lost in it, but I’m not sure that’s a good thing. 
Phil and others have spent a lot of time in that labyrinth and might have some additional thoughts, but, as he note, that’s for a different thread.
- as far as this question:
Is it even worth learning any of the current smartthings stuff at this point?
It’s really hard to define what “current“ since Samsung missed their own announced timeline for cutting over from the old architecture to the new architecture, and there’s no new timeline specifics announced, so who knows what will be working when? Some things are only available in the old architecture, but a lot of the new architecture is still in beta and there are glitches and frequent changes.
I don’t think it makes a lot of sense to spend time working on groovy, whether it’s for smart apps or DTHs, unless there’s a specific device that you really need to get working in the next few weeks and it’s not supported in the edge beta yet.
There are a number of community members who have begun developing edge drivers (written in Lua instead of Groovy), but again, everything is beta and there are glitches. So it’s interesting, some of it can be used right away, but you will be spending time on something which is changing frequently. That would be worth it to some people, but not others.
The following thread might help:
FAQ: I have no idea what Edge is. Is that a new developer tool? (2022)
- Zwave direct association is part of the independent third-party specifications for Zwave. It’s useful for some situations and feels kind of out of date for others. It’s been around a long time. The biggest issue with it is that you can’t make the triggers conditional like you can with scenes or routines. So if you set it up with a direct association so that this motion sensor turns on that light, then activating that motion sensor will always turn on that light, regardless of time of day or who is home or any other conditions.
Personally, I think Zwave direct associations are most useful for auxiliary switches in a three-way set up, because I personally can’t think of a situation when you wouldn’t want the auxiliary to turn on the Master. ( and I’m really good at thinking about use cases. 
)
Zwave direct associations will work even if the hub itself is broken, again, good for three-way light switches. But they are just a very primitive form of automation.
They are also popular for multi button wallmount or handheld switches, again, because if you want a double press on that switch to turn on a specific light, you want to do it every time: you’re not going to wrap a conditional around it.
But Z wave direct association can only be used between 2 zwave devices and only if they are at the same security level.
Most of the other automation methods available to you on the SmartThings platform will let you work with any devices of any protocol that are exposed to your smartthings account. They don’t have to both be z wave.
So… Z wave association is part of the protocol and some manufacturers do rely on it, particularly for multi button remotes. It’s good to know about it and you may want to use it for some specific devices. But it’s not something you’re going to use most of the time, it’s just too inflexible.
Regrettably, from my point of view, from the very beginning smartthings made the decision that they were going to make anything which was specific to one protocol pretty much invisible to the end user In the official features. They thought this would be less confusing, I think it’s just frustrating. It means that the official UI doesn’t offer an easy way to create associations or set up zwave central scenes, or identify Zigbee groups, or really anything which is protocol-specific.
right now, for example, the official response from smartthings have been that they don’t even know whether you will be able to set associations with an edge driver, which to me is bizarre for a hub which is a certified Z wave controller. However, as @philh30 noted, it can be done. But I doubt if you’ll find official documentation on it yet.
Anyway, you just happen to hit one of my own hot button issues, which is that multiprotocol platforms should provide more options, not fewer, but that’s just my own philosophy.
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If you want to talk more about the issue of what is worth researching right now, that’s getting pretty far off topic for this particular thread, so you can either start your own thread or join one of the existing conversations about development for the new architecture.