Well apparently after my post that basically said READ you don't plan too so here is a bit of spoon feeding:
1. Yes you can reduce monitor timings in CRU or NVCP by changing the blanking period and/or total pixel count to establish a more viable pixel clock(preferably under 470mhz) This can be found under the "manual" ssection of NVCP for custom resolutions or the timings section in CRU using a custom profile. YES you need to read and know what these numbers do before messing around.
2. I and many use custom timing settings to eliminate overclocking side effects like: retention(not burn), gamma shift, uniformity and others. Mine are optimized per my "optimize timings" post and i am sitting at 449Mhz which is within the 450mhz clock rate of the PCB(which is also posted as the EP269) See answer to question 1 to connect some dots if you have not read it yet.
3. Yes some do this especially if they are worried image retention will eventually hurt their monitor. Also many like to avoid the "gamma shift" during browsing. There is nothing wrong with doing this and it can even help keep you GPU a bit cooler as the desktop will be half the rendering size.
4. NO you should not keep it at stocks. If you were going to play it safe you should have bought a main stream, pre-calibrated, uber warranty, store bought sheep machine. Do more reading and find out a little about the product you have and how to properly bring out its potential. However you can if you want because it is your monitor,
Hopefully you don't take this overly serious and it helps you a bit