Regarding my O2 - I can't say what is, or is not accurate I am afraid; I have rely on others for that, and so try to be supportive of those more knowledgeable than myself.
Firstly, the model looks nice in that it is attractive and detailed. I have a Maunsell green Southern Railway one numbered '207'. This, I believe, fits in with the date of my fictional layout, which is 1933. (About 1930 the SR started dropping the initial 'E', 'B' and 'A' to indicate whether they were former LSWR, LB&SCR or SECR, and adding 2000 to the numbers of the former LB&SCR and 1000 to the numbers of the former SECR locos.)
It was packaged well, certainly well enough for it to cope with the combination of Royal Mail and Bulgaria Post.
Let me stress that it runs well now, and that I am currently very happy with it. However, when I first ran it, it almost went straight back to Cornwall. It would derail on my 30" radius scenic curve. Fortunately, on another forum, the reason for some of the O2's misbehaviour had been high-lighted. Some of the O2s had the back-to-backs of the driving wheels set a little too wide. The suggested cure was to put a OO back-to-back gauge between the wheels and squeeze the wheels into it with your fingers. Luckily, I had a DCC Concepts back-to-back gauge and was able to do it. It worked like a charm. Instant and massive improvement!
Running-in seemed to help quite a bit, as well. I recommend that you do so.
Another thing that I should mention (although it was the fault of the layout and my clumsy ballasting rather than the model) was that the O2 would sometimes take exception to tiny grains of ballast stuck on the insides of rails that other stock had ignored. Easily sorted by identifying the places and scrapping the specks of ballast off. If you are as ham-fisted as myself, you may want to be aware that you might want to check for ballasting malfunctions.
Have to put my hand up to my track-laying not being perfect. However, the O2 now goes through all the points in both directions, straight or curved path with no problems. There is one set of points that my Hornby M7s don't like going through the curved path in the toe-to-heel direction. No problem with the O2, which means that it tends to get lumbered with the goods train when running the layout in Western Division mode.
The O2 has a coreless motor. The advice given both in the instruction leaflet and by Dave Jones on a certain other forum is not to use either DC feedback controllers or 'electronic track cleaners' such as the Relco ones, or the Gaugemaster HF1 or HF2 with it. I use the Gaugemaster HF1 on my layout. It has inputs for the controller output, and for the 16 volt AC accessory to power the clever electronics. All I did was to put an on-off switch in one of the 16 volt AC leads so that I can turn the 'electronic track cleaner' off when I run the O2.
You need to hear from a DCC user about the DCC capabilities rather than myself. However, the smokebox door comes off easily; I think that the DCC socket might be there.
The cab can be taken off (the instruction leaflet tells you how) to let you stick crew in. The 'coal load' comes off the bunker easily, which can make sticking bits of real coal in more interesting than usual, although not impossible. What you can't do without damaging factory-fitted detail is to remove the body. So far, I haven't had to try to add weight, but please be aware that I run short trains. If your ambition is to add battery powered radio control then that might well be an issue.
My O2 seems to pick up from the driving wheels only on one side. Because I use live frog points, I only found that out when I cleaned the wheels. Don't know whether that is a one-off fault, or whether it is more common. Doesn't bother me, though.
Some experienced and clever modellers on some other forums have formed the opinion that the O2 uses the 'split-chassis' mode of construction.