THe newest version of forge (1.12 - 184.108.40.2069) with optifine (OptiFine 1.12 HD U C3) doesn't work that well, my game's keep crasing after phase 3 of forge loading:
The game crashed whilst initializing game
1. Always post the FULL crash report
2. Don't use Optifine if it crashes. MC runs fine (usually) w/o it.
"We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far."