Well, I had to do some research here.
The average car/moto headlight is 700 lumens, the taillight is 100 (which a car would have at least 2, probably 4).
On all my bicycles, I use a 7lm rear light, which I thought was enough lights, but to my surprise, there are several 100-250lm rear lights. I also have a Cycliq rear camera which also puts out 100lm.
There are no regulations about rear light brightness or patterns: the only regulation is many areas require cyclists to have lights at night but no specifications.
The goal for rear lights is simply to be noticed by drivers. I'm not personally worried about if they can gauge my speed, despite sharing the road vs being in a separate bike lane. I don't think the speeds of casual riders, 10-12mph, vs my commute speed, 16-20mph, makes much of a difference to drivers.