alright man. the best thing i can tell you for now is too read...read....and more read. haha
there is so much info out there on this that you could answer most of the questions yourself
but lets see....first things first....start with a little shot. don't just start with the highest...get used to the little shots and step up to the bigger ones.
bottle heaters are used for heating the bottle

. you want a bottle heater based off of pressure not temperature. this just allows the bottle to stay at optimal pressure for when you spray. usually around 1000 psi or so...right guys?
and yes...if you want to spray every gear then you will have a WOT switch at which point the nitrous will activate when at full throttle. but...i strongly advise a window switch. this will allow the nitrous to activate only at a certain rpm....say 3000 to 6400 or whatever you set it too. that way if you miss a gear your engine won't go BOOM!
and yes...at any point the rpm is in the range and at WOT nitrous will spray....
well i answered most of your questions....haha..but still search and read! its a great tool. i know because i'm installing nitrous and 00vi at the moment.
good luck!