I've taken a look at AM4 M-ITX boards and, while there are a few of them, the ones you're probably more interested in have something weird:
Asus has two ROG Strix models, one with the B350 and another with the X370 chipsets, but neither of them seem to have video outputs? https://www.asus.com/Motherboards/ROG-STRIX-B350-I-GAMING/specifications/
You'll have to use another brand or go with Intel.
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.