This paper presents the outcome of ray tracing simulations for different optical schemes to be setup at the European X-ray Free Electron Laser facility (XFEL.EU), Germany: one- or two- channel (cut) crystal X-ray monochromators (K-Mono; using spontaneous radiation) are planned and designed mainly for photon beam based alignment, which is gap tuning of the undulator segments and phase tuning of the phase shifters during commissioning and maintenance of the undulators. The coherent SASE (Self Amplified Spontaneous Emission) radiation will be monitored pulse-resolved by single-shot spectrometers of which two types are investigated: i) a three element spectrometer, design proposed by Yabashi et al., which consists of a curved focusing mirror, followed by a flat analyzer crystal and a 2D-detector.ii) a two element spectrometer based on a reflection zone plate that reflects and focuses in one step, and a 2D-detector (currently under development).