The whole point of the kit is to use the supplied harness with relays. The kits have heavier gauge wire to supply the increased load of the H4 lamps. The factory light switch is not designed to handle that amount of current, so it is used simply to supply the trigger current to the relays which handle the additional load. So of course you need to use the relays.
Both kits (Toyota or Crackedback's) are designed to simply plug into the existing harness connectors, with the only wiring addition being a fused power supply (bat +) and a ground. Any mods to the harness would simply be to clean up the installation, not for functionality. And Crackedback's harness (as he previously said) comes custom tailored to your application.