The answer to your ? is, there is no standard formula. There is theory, but the only way to get any particular model set up with the "correct" offsets is to fly it, see how it flies, adjust right or down thrust if you think it's called for, and fly it again. I say "correct" because it's a matter of flyer judgment whether it looks and feels right or not. KWB cites the standard rule of thumb, 2-3' right and 2-3' down as a starting point. High wing requires more downthrust, mid-wing & low-wing less or none at all.

It's usually not practical to produce offsets at any precise angle. It's normally done with one or two or three metal washers under the appropriate mounting holes. So if one washer isn't enough, and three is too much, you're stuck with two. I have on occasion sorted a pile of washers by thickness, or shaved a washer with a file.

Some kits will have offsets built into the firewall, which in my book is a mark of a well developed design, but even that only works well if your engine is similar to the prototype.

Lots of guys fly happily with zero thrust offsets, and for sport flying you can get away with it on most models. But some designs coupled with some engines produce an extreme reaction at high torque/low airspeed. I have seen models snap-roll right over and into the ground on take-off, which is the worst scenario. Once you have good airspeed, the effect subsides to unnoticeable.

With G2 you can edit your offsets by tenths of a degree and observe the simulated effect. Try the Dazzler with 52 4-stroke. Fooling around with that for a few sessions will help you a lot more than theory.