Is the SkinMC Mod compatible with Optifine/Optifabric

No, unfortunately it is not compatible with either Optifine or Optifabric.

We recommend the following as a replacement, and often better performance:

• Sodium: https://www.curseforge.com/minecraft/mc-mods/sodium 
• Logical zoom: https://www.curseforge.com/minecraft/mc-mods/logical-zoom 
• Shaders: https://www.curseforge.com/minecraft/mc-mods/irisshaders