The right question is how visible a light you need for daytime use - IMO a blinking light is going to be more noticeable than a solid, bright light. And blinking just needs to be seen at sufficient distance to make you visible to oncoming traffic.

As noted by others, if you're on a path without automobiles it's not clear you need any light, but certainly less bright than one you'd want for the road. I have a Bontrager ION light. It is plenty bright for visibility on the road. It also comes with a low power mode that blinks at much lower brightness. While I'm on the road I use bright, but on a trail might use the lower setting.