DitDit

Hello, I recently downloaded the Technic Launcher, and I am mostly happy with it! The one thing I would like to know about, is if it is possible to install custom vanilla Minecraft versions, like the Optifine 1.12.2 version? I would like this because I don't want to wait for Forge too load with something that could load without Forge. I've tried all I can think of, and need some professional advice. Thanks for all help!