For me I first aim my light
For me I first aim my light against a wall. This gets me in the ball park as to where they need to be. It also let's me observe the beam pattern & check for how much stray light there is. It is important to check these as it is possible in some cases to get bulb positioned wrong or even if correct placement manufacturer may not have proper depth set. I have had this happen many times where bulb was not manufactured with proper depth to get proper beam pattern.
Important to the nature of the beam pattern is the placement & type of LEDs used. Use only bulbs whose chips size & shape mimics the size & shape of the halogen filament. Do not use othe designs as the beam pattern will absolutely not be correct & you will blind people if used in a low beam setting.
Low beam cutoff line should meet the road 60-75 feet in front of car in your lane. With some fixtures there will be a drop as your cutoff meets the oncoming lane. In this case cutoff should meet road in oncoming lane about 30 feet in front of you. Cutoff will continue to rise after it reaches the fog line but at fog line cutoff should meet road no further than 75 feet.
This will give optimal results for both beams for prius H4 headlights & will not blind other drivers assuming clean clear fog free non oxidized lenses. Dirty oxidized lenses scatters the beam blinding others even if otherwise properly aimed.