So great to have you out, Alex!
I recently bought one of these and it hits all the markers:
https://www.mec.ca/en/product/5061-830/ ... Bike-Light Right now it's effectively backup to my primary light:
https://lightandmotion.com/collections/ ... -comp-1500
I tend to use a lower, more sustainable 200-500 lumen setting for most of a ride. But for the more technical bits of darkened forest, it is quite important to be able to bump up to a higher 1000+ lumen setting.
I also recommend having a second light on at the front at all times (even just a little cheapie.) We've had a few riders suffer a light failure and be plunged into blindness, at speed, in a rooty forest!
One rider had their light fail while leaning into a corner in the dark. She didn't even know she was falling until she landed on her shoulder (and broke a rib, I think.)
The other benefit of having two lights is you can keep your brighter one aimed farther ahead so you can adjust speed and gearing appropriate for the overall trail profile, and your backup can be aimed down closer in front (2-4m) to help you maneuver past roots, rocks, and bits of terrain.
Some people really like having a helmet-mounted light, because it lets you scope out trail entries and features, without having to aim your bars. This is especially needed if you're unfamiliar with your route and you're way-finding in the dark. It's less important if you're following taillights.
Finally, lights are like tires and tire pressure: commonly subject to overthinking. I'd say get something 1000 lumens and you're good to go.