The author of EMAN2 is incorrect, I don't know why they claimed that. ChimeraX is probably like Chimera and targets a 30fps but can drop below that significantly based on dataset size and rendering quality. It should be using OpenGL with display lists (or some more modern variant on that). The main loop is likely in Python, but if you're just moving a molecule around, the rendering should touch very little python. On a modern machine with an nvidia gaming card it should be fine.

For example, in this case I loaded 2PLV with "open 2PLV" and on the right side, there's an option to select one of the mmcif assemblies, with select 1 being "complete icosahedral assembly, 60 copies of chains 1-4". With the default ribbon rendering, rotating is completely smooth; with all atoms displayed (wireframe or sphere), it's still smooth. Computing a surface for the entire capsid takes well under a second(!) and still renders smoothly. Rotating shows my GPU (nvidia RTX 3080 Ti) at about 50% utilization, and if I exit Chimera, my GPU's releases ~200MB of memory.

Chimera was never intended to do high quality rendering of cellular environments with many hundreds of proteins. It was intended for a combination of nice rendering and scripting directly in python. VMD definitely handled some extremely large scenarios faster. A dedicated small C++ using modern OpenGL would be able to do far, far more than Chimera when it comes to simple rendering without any scripting control.