You have to understand the effect of these offsets and decide based on the style of flying you enjoy with the specific model.

What am I talking about ?

Example ___
Normally a model is setup with incidence angles (decalage) such that it flys hands off with neutral control surfaces at a specific speed and power setting.

Now about your style of flying; normally an increase in power is used to establish a steady rate of climb but you may wish the result to be remaining at the same level and just gain speed.

When doing aerobatics you may wish a loop to be in a vertical geometrical plane and have a minimum of effect due to full power on the way up and lower power on the way down and out of the loop.

Like many already said the final settings are done by actual flying.
The stated values on drawings or manuals are just a starting guidance.

Have fun experimenting.

Zor