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EDIT: Actually I can provide some answers to the above post.
You're on G.INP, before you changed your DSL settings you must've had G.INP support disabled on the device. This would cause interleaved mode and a rather high ping (possibly combined with a reduced sync rate too).
Regarding the annex A and B, there's two types of annex in VDSL2.
BT uses frequency band plan Annex B Plan 998ADE17, however the setting should be Annex A in the actual DSL settings as that annex setting refers to whether it's running over POTS or ISDN (POTS being A, ISDN being B). At least from memory I'm pretty sure I'm right.