The triggerplate goes flush to the contour of the stock. You have to bend it to get there usually. Then you add to the triggers or remove metal to make them the proper height. As for position, the set trigger screw usually is centered on the sear arm & that should get you to the proper position for both of them to work.
And I will add, Mikes tutorial is great, no doubt about it. However, to build a rifle & do it compentently & to answer much more questions that come to mind when building a rifle, I suggest you buy a builders book. My favorite is Gunsmiths of Grenville County, however Chuck Dixons book is good also as it Recreating the Ky Longrifle.
To me, building a rifle without a book is like building a house without a plan. It may be a house when done but it may fall in on ya to......... :hmm: A good builders book will answer Hundreds of questions that come up.