I just put an order in for my first AR as well (a plain 6920), so I am also interested in this topic. Hope you don't mind if I piggyback some questions in here.
Are any of these AR wrenches or tools needed for the average user who will be using the rifle "as-is" and not doing multiple builds, etc? What about tools for general thorough cleaning? I already have all the rods, brushes (chamber and bore), CLP, etc.
I see "gen 3" PMAGs all over the place, but "gen 2s" also seem to still be on the market. Is there a reason? Why would one prefer one PMAG type over the other?
I also ordered steel GI mags. Are these more or less desirable than aluminum ones? What was the original spec?
To answer the OP and other on-topic questions and not drift into "mine is better than yours"...
If you do not plan to disassemble past user level maintenance, you do not need more tools that what you already have. Wrenches and specialty tools are for those assembling from kits or swapping major components.
The only tool that comes in handy as an extra is a sight tool. While sights can be adjusted with the tip of a bullet, a sight tool makes it far easier.
As for cleaning, the only thing a basic non-AR kit wouldn't have is the chamber brush. You can get by without one but cleaning is much easier with one. It has been my experience that GI chamber brushes have different threads than commercial cleaning kits and since GI cleaning kits are so cheap, I recommend all AR users get one.
+1 on the ruptured case extractor.
As for mags, I am not a fan of plastic mags and use GI mags. That is a choice you would have to make if you use afer-market accessories. Oh, GI mags are aluminum.
The sling as mentioned by Taliv is a good one and I will add that to basic load out recommendations. I will say, nothing fancy though. Basic GI web sling is good for most applications. I personally use a Vietnam-era sling. They $6 new-in-wrapper in my local surplus store and work perfectly fine plus I can tell mine apart from the 40 other AR rifles sitting in the rack at the range.
One other thing I would like to add is a drop bag of some sort to carry spare mags and a place to put empties. If shooting at a range, this may not be all that handy but were I live, we have lots of open BLM land and I spend a good deal of time out walking around especially when shooting whistle pigs.