Thing is there are so many other lights at night, especially at a roundabout, that I feel like the lights on bikes don't really stand out. No matter how powerful, a tiny light isn't as significant as all the headlights around. I think people get a bit dazzled, plus they're not concentrating to look for bikes. IMO there's no number of lights or things to make yourself safe, short of also being in a car. I approach night riding under the assumption that nobody has seen me.
One thing which I think is quite good is to get some of those snap on wrist reflectors. If you stick your arm out to indicate right/left, it's really hard to see in dim light, but a reflector (or a light I suppose but never see a wrist light) is much easier for drivers to notice.