Electric propulsion concepts involving electron cyclotron resonance excitation for plasma generation eliminate the need for electrodes inside the plasma. Concepts, employing magnetic nozzles to accelerate the entire plasma for thrust production, remove the necessity for a neutralizer. Two thruster concepts realizing such plasma production and acceleration are investigated: the well-known MINOTOR thruster prototype of ONERA and a new prototype under development at DLR called DEEVA. It is assumed that converging parts in the magnetic field lines along the plume direction lead to the weaker performance of the DEEVA prototype compared to the MINOTOR prototype. This study investigates the effects of magnetic field configurations on the DEEVA prototype, examining both a converging-diverging character and a strictly diverging configuration of the DEEVA magnetic field topology. The effects of these magnetic field variations are compared with the MINOTOR prototype using Langmuir probe measurements and thrust balance measurements. By observing trends resulting from operational variations of the prototypes - such as changes in input power, frequency settings, and volume flow - we can infer the influence of the magnetic field topology on plasma parameters and thrust. Potential improvements for thruster development are discussed based on the measured magnetic field topologies.