Alright ladies and gents, the day has come where optifine will now run with More Player Models and i'm going to walk you all through installing it. Before we start I would recommend a clean version of minecraft.
Step one, install forge 1.12.1 here. Download and run the installer for client. Once you have done this, open the minecraft launcher and edit your profile. Change the "Use version" and scroll down until you see forge 1.12.1, select it and save your profile. After this launch minecraft once to make sure forge is set up properly.
Step two, download More Player Models here. Then download Optfine 1.12.1 here, there have been reports of some versions of Optifine causing crashes, if that occurs download one of the alternate versions they have listed for 1.12.1. Once both are downloaded, open your minecraft directory (DO NOT RUN THEIR INSTALLERS). This can be found by opening any folder on your computer and typing %appdata% in the directory bar at the top and hitting enter. You should see a .minecraft folder, open that folder and locate your mods folder, if there is not a mods folder then create one. Once you find your mods folder drop both jar files for More Player Models and Optifine in this folder and launch minecraft with your forge profile. You're done!
As for the resource pack, just download it from here then activate it in your resource pack menu.
(Please only use the provided links or the mods may not function together. If a link breaks please inform staff)