The default brightness monitors ship with is always intended to make you go blind
The first thing that needs to be done is reduce it. It depends on the monitor, but the majority of monitors will need to be adjusted to somewhere between 10 and 30 to be usable. I use 23 on my current monitor, and in my previous one I used 12. The best setting is usually determined by opening up a web page that has a lighter background with black text on it, and then you reduce the brightness to the point where reading the text becomes most comfortable. A good page for this is Wikipedia's main page:https://en.wikipedia.org/wiki/Main_Page
I also adjust the brightness during the course of the day. At night, I use 23, at day I use 30.
The response time setting will not have any effect on input lag (at least not without using a 1000FPS camera to measure it; it's certainly not something that can be perceived by humans. It's like a 2ms difference or so.)
Anyway, this setting controls the amount of pixel overdrive applied to the panel. The effect it has is visual. Low settings will result in a slight blur trail behind pixels. The maximum setting will result in a trail of inverted colors behind pixels. The medium setting is almost always a good balance between the two and results in the least amount of "ghosting" possible, and is usually the setting the monitor is supposed to be used with.
We have an article on overdrive here:https://www.blurbusters.com/faq/lcd-overdrive-artifacts
And we also have a test where you can find out what the best setting for your monitor is:http://www.testufo.com/#test=ghosting
Make sure your browser page zoom is 100% (meaning no scaling is done by the browser) and then play around with the "response time" setting of your monitor and see which setting results in the least amount of ghosting.
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.