Thanks for you response.

In terms of Safari calc(px + vw) support, I haven’t noticed too much issue there based my own experience and (http://caniuse.com/#feat=calc). Happy to see some examples though.

For how big 1 responsive pixel actually is, it’s really up to you. I should’ve made it clearer in the post that I was given mock-ups of an iPhone 6 screen size. And my 1 responsive pixel combination represents very close to 1px on a 375 * 667 screen. You can always adjust the scaling too based on your design needs on bigger screens. I will update my post to reflect that. :)