It seems this is an emotive subject and for once, I didn't start it!
Having said very recently, probably in this thread, that I don't need to wear earplugs, I put them back in for my ride home tonight. It's the wind noise. The Schuberth is a quiet helmet but once you get above 60mph the decibels do go up. If I know I'm just going to potter about on some country lanes, I won't bother with the plugs, but on my commute there is enough time spent at high speed to warrant them. That means that in the city I'm relying on my vision mostly.
With vision in mind, I also think you can over-do it. Too much hi-vis, too many lights and people can get drawn to you like moths. The reason it's so dangerous to stop on the hard shoulder of a motorway is that people look at the stationary vehicle and unconsciously steer towards it. You tend to go in the direction you're looking.
I believe that whether it's noise or visibility it should be kept in moderation. Observation is key. Sound can be deceptive. Too much light or contrast can dazzle or distract. You want to be seen but kept in the context of all the other things that are happening. All this "look and listen to me" puts both the individual and other road users in danger. Distractions are bad. Allow other road users to take in the whole scene and there's less likelihood of an accident. It does require people to observe and pay attention though.
I don't think we can rely on being seen or heard, no matter how loud or fluorescent we are. The only way to have any chance of survival is to make sure there is enough space and time to react to not being seen. Keep relative speeds low and do your best to anticipate.
COAST:
Concentrate
Observe
Anticipate
Speed
Time
I like to ride fast and have fun, which is still possible if you keep COAST in mind. I'm not a mnemonic junkie but I think that one is worth it.