I have been getting the same issue with optifine where some of the blocks are invisible like the botania flowers, I will try turning off Fast render and see if it works.Optifine is working for me. Do you have Performance->Fast Render set to OFF? Having that on was causing me texture issues but everything was still rendering, so not sure why textures are not rendering. (assuming you mean by not rendering that the blocks are completely invisible)
Also try using Fastcraft. Even without Optifine, Fastcraft can get me 60+ FPS.
Turn off Vsync. Vsync actually lowers your FPS a good amount.