I remember with mechanical trims it was standard practice to retrim the plane after flight. This doesn't just apply to the first flight as its not an exact science, it might take several flights to get it right. Of course if you're real fussy about getting the plane to fly exactly level hands off, this will require trim changes on every flight as conditions change....

These days, instructors often don't mention adjusting for trim changes as a lot of people have computer radios and the trim values are automatically stored. The bonus being that they can't be accidentally knocked when the radio is switched off.

Anyway, all this is largely irrelevant..... a sudden gust or crosswind can push a plane off course easily whether it is in trim or not. In mode 2, the way to handle take-offs (in my experience, which isn't much) is to control speed direction (throttle/rudder) with the left stick until the plane is nearing flight speed and be ready on the right stick in case the plane wants to bank. In short, pay attention to what the plane is doing and fly with the sticks, ignore the trims.
When the plane is safely up a couple of mistakes high, then it is time to deal with trim problems.....