Hi. 

I considered to buy a TD-W9970 V4.0. I have seen lots of devices on ebay but they explicitly mention Annex A.

I could no really find anything in the documentation for changing Annex, except for older versions.

Will a TD-W9970 V4.0 in general also support Annex B?

Some offers also say TD-W9970 V4.0_B (while still also mentioning Annex A).

Does the "B" mean Annex B support? Or is is some additionally modified version of V4.0?

Or do you really need the TD-W9970B? There only seem to be older versions+firmware for this though.