I think it depends on each case from what it sounds. My fiance's interview was last week (I was there...in the process of doing a review right now), and even though I brought every conceivable bit of financial info for him to present to them, all they wanted from was my employer's letter and the main 134 form. I have a feeling it depends on what they see on the form with a quick glance and they judge it from there regarding what they want more info on?
BTW, I'd say originals of the employer letter and bank letter as asked. With other things, get originals where you can, but sometimes the only original is a printout of an online statement.
orangeneko got a reaction from Nich-Nick in London embassy questions.