Additive manufacturing synthesis using laser engineered net shaping (LENS) is utilized to rapidly print libraries of mischmetal (MM = La, Ce, Nd, and Pr) containing RTMB alloys (R = MM + separated Nd and TM = Fe and Co) enabling robust evaluation of physical properties over a wide composition range. High throughput characterization of the magnetic and thermal properties are used to identify compositions for potential high temperature, high-performance permanent magnets with reduced critical rare-earth elements. Improved Curie temperature (T~500°C) is obtained with substitution of Fe by Co in pseudo-ternary RTMB alloys. Furthermore, a four-fold decrease in the Nd content can be achieved through substitution with less critical Ce- and La-rich MM, while retaining high T. Guided by the properties of the LENS printed samples, selected compositions with and without TiC additions are synthesized via melt-spinning techniques to produce nanostructured ribbons. The maximum room temperature coercivity (H) and energy product ((BH)) without TiC are found to be 5.8 kOe, 8.5 MGOe, respectively, while TiC additions as a grain refiner gave H and (BH) of 4.9 kOe, 9.8 MGOe, respectively. Structural characterization of the melt-spun ribbons shows homogenous grain refinement with TiC additions, which leads to an increase in the energy product.