I am not really into this 3D thing. I just follow what others have done before, sorry if I can’t help much in this regard.
It seems I just have had a better luck to build my own image and run in 1920x1080 res which is workable despite most users report issues with this resolution. Running with 1920x1080 generates lots of heat and I still have minor issues with my build like tty framebuffer login (the one you type when you are with ALT+F1) is displayed over the desktop area and they share same keyboard input. My build use kernel 3.4.x
If i can fix this i may share the image if you can live with a low score (maybe not as low as you have now so you can get some improvement), for now, it is just PoC.
Technically the H2+ can display 4K so FHD desktop should not be a problem… Maybe it is just the mali version in use, who knows. Perhaps you can try more recent mali: https://bootlin.com/blog/mali-opengl-support-on-allwinner-platforms-with-mainline-linux/ but with mainline kernel.
BUT if you share some 3D C source code and can compile and see if it works or how it works (speed) and if the build worth a try.