You could check out the following links if it helps:
I think of something like this:
Understandability of the entering mode: either Parent, or Children
Eliminate undefined state and possible confuse, when there are some values in the Children nodes, and the user enters Parent value
Clear UI due to hiding non-relevant input fields
Jumpy behavior of the switch control. The effect should be ...
I found this question asking myself the inverse question:
Why do Haussmann style buildings in Paris have 5-7 floors, not more or less.
Haussmann was active 1853-1870. Commercial electric elevators only became common in the late 19th century. So the Haussmann style may give away how many floors a user could be expected to walk up.
That said, there may have ...
If I understand your question correctly you are talking about super thin fonts and their contrast requirements.
There are no requirements if a font is super thin in terms of WCAG, 508 etc. that are any different than normal weight fonts.
That being said, it isn't about requirements (and too much focus is put on requirements and not enough on the end user).
Yes it should be the first item that gains focus, even before 'skip links'. It is the only use case I can think of where 'logical tab order' does not apply.
As you mention WCAG I will presume you mean websites. (you should actually look at ATAG as that is likely to be more applicable.)
As long as you can reach every function by keyboard then your application / site is accessible by 'the rules'.
Job done right?
It may be enough to meet the legal requirements or minimums, but we should change our thinking to ...