Both VTA and VTF matter.
VTA adjusts the angle of the stylus in the groove, more critical with line-contact styli than with conical or elliptical.
VTF does two things: ensures sufficient force for good tracking, and varies the physical relationship between the coils and the magnets to optimize their electrical interaction. The manufacturer's recommended range is intended to maintain this alignment in its sweet spot, but your most accurate measuring tool is your ear: listen for the best results in the time domain (e.g., least smearing of transients).
These adjustments are interactive, since changing VTF will also affect VTA by increasing or decreasing the deflection of the suspension.



