What vehicles may you overtake when this traffic sign is displayed?

Your choice (answer 1: “No vehicles”) is correct.

This sign means “overtaking prohibited for motor vehicles with more than one track.” In practice, that means a car driver must not overtake any vehicle on the road, because overtaking would require your multi-track vehicle (your car) to pass another road user. The prohibition applies regardless of whether the vehicle in front is a bicycle, a moped/motorcycle, or another car.

Rule of thumb for similar questions: When a prohibition is aimed at your vehicle type (here: multi-track motor vehicles), you must not overtake at all until the ban ends (end sign, or a new rule such as an intersection/zone change where the restriction no longer applies). Only drivers who are not covered by the ban (for example, single-track motorcycles) could still overtake, if it can be done safely.