The first image shows a set of pin driving FETs. The fact that you misidentified/couldn't recognise that means you have a lot more to learn before trying to do any transistor-level RE.
I agree, I have *much* to learn. Do you have any suggestions on how to start? My usual way is to dive-in and see where it goes. I find that silicon-level IC design and layout is not exactly the kind of topic people are talking about on forums, blogging about, etc. so learning and getting feedback has been hard to come by so far. I have books on the topic, and I have been reading them, but books cannot tell me if my understanding is correct or if I'm interpreting some part of a die-shot correctly, etc.
As for the counters - does it matter? They could be using inverted logic. XNOR chains, or something else. The only thing that matters in simulation is whether the outputs are correct.
It probably does not matter too much, but when possible I like to describe the hardware as accurately as I can. I tend to find that the designers of the real chips put a lot more thought into the silicon, and the way they did things was probably done for good reason, made things simpler, or worked better than some other method. If there is a nice side-effect of counting down vs counting up, because one method lends itself to nice coupling with other functionality, then I'm really interested in learning and understand that detail.
Another reason is that I find when making assumptions, or doing something differently, when trying to make a reproduction (or emulator, simulator, or whatever term is preferred), it is very easy to introduce errors that are sometimes really subtle and hard to find.
In this case, the direction of counting also helps explain how and when a register update from the host computer actually affects the counter. Does it happen immediately, or does it happen after the current cycle? There are also two parts to the counter, and does changing the MS-bits affect things the same as changing the LB-bits?
Some of this can be characterized, and people have done a lot of good tests to suss out some information. But, when decapping has been done and die-shots are available, some of the assumptions can finally be definitively confirmed, or not, and everyone benefits.
Rather than expecting someone else to do the work, I like to contribute where I can. In this case, unfortunately, I have a big learning curve in front of me, so I was reaching out for some guidance in trying to get my bearings.