  High frequency (millisecond) quasi-periodic oscillations (HF QPOs) are
observed in the X-ray power-density spectra of several microquasars and low
mass X-ray binaries. Two distinct QPO peaks, so-called twin peak QPOs, are
often detected simultaneously exhibiting their frequency ratio close or equal
to 3/2. Following the analytic theory and previous studies of observable
spectral signatures, we aim to model the twin peak QPOs as a spectral imprint
of specific dual oscillation regime defined by a combination of the lowest
radial and vertical oscillation mode of optically thick slender tori with
constant specific angular momentum. We examined power spectra and fluorescent
K$\alpha$ iron line profiles for two different simulation setups with the mode
frequency relations corresponding to the epicyclic resonance HF QPOs model and
modified relativistic precession QPOs model. We use relativistic ray-tracing
implemented in parallel simulation code LSDplus. In the background of the Kerr
spacetime geometry, we analyze the influence of the distant observer
inclination and the spin of the central compact object. Relativistic optical
projection of the oscillating slender torus is illustrated by images in false
colours related to the frequency shift. We show that performed simulations
yield power spectra with the pair of dominant peaks corresponding to the
frequencies of radial and vertical oscillation modes with the proper ratio
equal to 3/2 on a wide range of inclinations and spin values. We also discuss
exceptional cases of a very small and very high inclination as well as unstable
high spin relativistic precession-like configuration predicting constant
frequency ratio equal to 1/2. We demonstrate signifiant dependency of broadened
K$\alpha$ iron line profiles on the inclination of the distant observer.
