Is there a right model or version of this unit with regards to the area of data center or the volume of room it is installed

Any temperature monitor will only accurately measure the temperature where it is located, that is the ambient temperature. In a datacentre or server room, there are a number of temperatures you may wish to monitor, for instance at air outlets, in hot and cold aisles, or temperature gradient for instance at the top of racks and at floor level. It can be likened to building a contour map, the more measurement points the more accurate the thermal picture.