someone explain powerlimit to me.

In my personal opinion, overclocking is only useful when you're working with last-gen hardware playing new-gen games. You bought a brand new GTX 9- series card, I would not risk pushing it until you have to. you'll get what, 15 frames more? at the cost of stability and lifespan of the hardware? its not like suddenly the VR functionality is unlocked for you, so just leave it be.

If you want more functionality then push your budget, don't buy a Honda civic and put a racecar engine in it, you'll strip all your gears. once games start challenging your card, then maybe work with some overclocking. that way when it dies you have next-gen options.

as far as '%110 power - %90 lifespan.... this is absolutely not accurate. there are more factors involved than you will be interested in, so think of it as an exponential. maybe %110 is about %90 lifespan, but %120 is more like %60 lifespan, %125 more like %50 lifespan.

get a water-cooling system and you might be able to push it further, but then you'll be restricted by the speed of your CPU, Motherboard, and RAM.

Finally to answer your question. "power limit" is exactly what it sounds like. overclock the timing on your card without supplying power, and the card doesn't have the juice to run games in a stable fashion. bump it up too much and you run the risk of stealing needed power from other components, or a power surge in the event that you don't have a top-of-the-line power supply, based on the fact that you went for the 960 instead of the 70, I doubt you bought a superior quality PSU. "Power Limit" implies that it does not draw max power all the time (duh) and so any sort of incompatability will simply come in the form of a crash / bluescreen when trying to run games at higher settings than you should be.

bottom line, deal with your budget card until you can save up for the GTX 1080, it's blowing it's price competitors out of the water. now THAT is a card you will not need to OC for years to come. if you don't get the results you expected out of your brand new card, your CPU is probably the weakest link in the chain. I got a buddy who has a GTX980 with the HTC Vive (I got the 970) but with my i7 running the backround threads instead of his two-generations-old i5, I nearly double his frames in the same VR applications.