RAT 5 you have to read a tad more carefully
As i said at the moment we operate purely Classics with the first NG arriving in around 10 days.
As i said above, it is recommendet to switch to manual flight before 400 ft AGL if you intend to do a manual landing, however you can happily let it fly down to 50ft and then disconnect for that, in fact that is actually trained to show us the effect of the trim up which is not at all hard to overcome if you are prepared. Of course that only applies to ILS, NPAs and visuals are flown with single autopilot or raw data. Raw data flying is heavily encouraged and i fly quite often into the london tma from cruising altitude manually and flight director off until touchdown.
Dual channel approach is recommendet because there is a possibility of a single channel autopilot hardover which actually happened in my company, if you use dual channel autopilot you wont get that but instead just a disconnect of both autopilots (every CAT D simulator can simulate that, just try it). As a plus you allways have automatic go-around capability and can allways switch to CAT II or III whenever you need to.
I have just rechecked and the autopilot actually may be used above minimum autopilot engagement altitude during take off, so 400ft in the NG is perfectly fine. That just recently changed in the ongoing standardization over the whole boeing fleet in our airline group and as i'm not officially trained on the NG yet (have to do a difference training consisting of CBT, selfstudy with a differences manual, written test, a simulator session and 5 days of supervision on the line) i wasn't really aware that with the NG our company now allows engagement at 400ft AGL.