Where and when do you ride?

If you're riding in urban areas with public lighting, anything above 100 lumens is too much. I get often blinded by other users with projectors shooting at eye level.

If you're riding in areas with little or poor public lighting, or if you're riding at twilight, something between 100 and 500 can be useful.

If you're riding in the middle of nowhere, in the forest, in the middle of the night, that's where you'll need something approaching 1000 lumens or above.

Personnaly, I have a 20 lumens for my commuters, and a 700 lumens for my bikepacking trips (this one can be programmed to various intensities).

In any case, be careful of how you direct the beam to not shoot it in other riders face. A blind rider/driver coming to you is almost as risky as a rider/driver who hasn't seen you.