In my experience, VNC is more stable, but when Termux-X11 works, it feels snappier than VNC, and the resolution of the Linux environment is automatically scaled to the available screen space you have (making portrait/landscape switches and soft keyboards feel seamless)
ClassiCube has a WIP GBA port, but according to commits it only hits 2 FPS as of now and is not listed in its README.
On a related tangent, there's also Fromage, a separate Minecraft Classic clone written for the PS1 (https://chenthread.asie.pl/fromage/).