THIS!

MTP sucks hard and is slow and easy to overload with many files.

My 4.2 device was Umi X2 Chinese phone and I even hacked together couple Roms for such Meadiatek based devices back then. I remember my lightest ROM was like 250mb. With working PlayStore and all, but obviously only bare minimum included. Nowadays even the lightest custom Roms are 700mb+ . With Google apps and all easy 1.5GB and more.