In that case, should I try to take off with idle (or 0) N1, so drag is reduced?
I have no idea what you're attempting to say here. Should you attempt to take off with no thrust or idle thrust?
Every engine has internal friction which reduces it's efficiency. In piston engines, the internal friction of the many moving parts is substantial. The actual output of the engine is substantially less than the power the engine is making; the largest share of power produced by the engine is taken overcoming it's own internal friction, drag, and inertia.
Likewise, a turbine engine overcomes internal friction from a number of sources, ranging from bearings to accessory drives, but the net thrust output is defined, technically, as gross thrust output, minus ram drag. Ram drag increases as a function of airspeed, and inlet drag is a function of mass airflow. Increase the N1, one increases thrust from the fan, one also increases drag. One gets more thrust out of the engine than drag, hence one has something that's measurable (and usable) as net thrust.
The engine produces a lot more power than what you're able to use, because a lot of it is nullified by the drag increase.
This really isn't that hard to understand. The faster one goes, the higher form drag, parasite drag, etc, increases. Transonic issues also come to bear on nacelle inlets just as they do on flying surfaces and every other part of the aircraft. Just as certain parts of the aircraft react differently and are affected differently by these effects, the engines likewise have unique changes in airflow, drag rise, etc.
Pick up a textbook. Read the definition of net thrust. This is hardly something I've invented. It's unfortunate that you find it confusing or disturbing. Perhaps it's new to you. It's none the less a basic definition and element of powerplant design, operation, and measurement. Net thrust is gross thrust minus ram drag. Ram drag is related to forward speed, as well as the engine operational condition. A windmilling engine doesn't experience the same ram drag (also often referred to as inlet drag or intake drag, which are related and part of the same value, but not the same thing) as an engine operating at high power settings.
This falls into somewhat the same type of category of misunderstood concepts as ground effect. Even today ground effect is being taught as a cushion of air beneath the wing, when it's nothing of the kind. Add to the same mythology the popular notion of reverse thrust in turbojet/turbofan installations, and mixture and carburetor usage in light piston airplanes...all commonly misunderstood topics.