Tradesman1 :
Boost is integral to the GPU, taking it above and beyond it's base clock, it still is there in the PRe OCed models and if you OC it's still there. GPUs are the same as CPUs, all are individual, i.e. some 1080 GPUs OC great others not really, so one advantage of a Pre OCed card is you know it's guaranteed to run up to at least the Pre OC that you don't have getting a reference card
All 1080 models pretty much overclock to the same level. Usually you would be right though, but now the limiting factor in overclocks is power delivery. Pre-overclocked cards aren't actually overclocked by that much. Boost isn't integral to a GPU, more like a feature. GPUs certainly are most not like CPUs at all.
As I said however, you are paying the premium for an RoG GPU (I think the Strix?) for the cooler and better power delivery, there is much more to a GPUs performance than just the core clock speed.
Going back to the topic, cards by EVGA and ASUS are very good. Look for a card that has had heaps of reviews to find out the experience that people have had, however going with EVGA or ASUS they won't let you down.