The energy resolution and position sensing with two types of pixelated anode designs of high pressure xenon gamma-ray spectrometer were investigated. The first design is composed of a single planar cathode and four anode pixels embedded in the center of a "non-collecting" anode plate. The second design is composed of a cylindrical surface cathode and seven pixelated central cylinder anodes. These designs remove the Frisch grid which can suffer from excessive micro-phonics in real-world applications. The distribution of electron cloud created by interaction between gamma-rays and Xe was obtained with Monte Carlo (GEANT4) simulations and shows the dimension of electron clouds increasing from approximately 0.1 mm to ~100 mm for gamma-ray energy range from 50 keV to 10 MeV in Xe at ~50 atm pressure (~0.5g/cm3 density). The charge collecting efficiency and waveform of induced charge on each anode were obtained by tracking electron cloud drifting. The position sensing based on both position dependence of weighting potential and the distribution of induced charge among anode pixels were also probed.