In theory, helical recording does not affect total capacity. A track will take up a certain area of tape regardless of whether the tracks are linear or helical. Helical tracking is used in VCRs because it lets you increase the speed of the head relative to the speed of the tape by a factor related to the width of the tape, thus allowing for a single track with very high bandwidth relative to the speed that the tape moves at.

FWIW, modern LTO uses linear, not helical tracking (but with 1000s of tracks).