Type into any field and everything else in that category updates instantly, no picking "from" and "to" first. Everything happens right here in your browser; nothing is ever uploaded or sent anywhere.
On pixels: unlike physical units, pixels only mean something once you know the resolution they're rendered at. That's what the "px per inch" setting above is for. 96 matches how CSS pixels behave on a typical screen; 300 is the standard for print-quality output.
No pitch, no pressure. Just talk about where you want to go.