In this article, we explore pixel optimization ways based on our electro-thermal model to reach spectral resolution of the order of 1.8 eV. We then use this model to manufacture a new batch of pixels on which we conduct experimental measurements. We measure the transient response, energy linearity and noise spectrum of our pixels with an Iron 55 source as well as an innovative on-chip pulse injection system. A low noise cryogenic amplifier as well as a cryogenic experimental setup have been designed to perform these measurements.