I have zero use for any wiring or outlets that aren't associated with my modem, so my plan is to disconnect all internal wiring at the physical splitting point of the internal wiring, other than the one going straight to the VDSL related outlet.
Image of existing wiring
That'l hopefully eliminate any internal wiring noise due to so much wiring going to redundant outlets (5 in total), and AFAIK, won't need a master splitter.