This tutorial for building custom, stylized Metahumans is excellent, although it requires the paid Mesh Morpher plug-in.
I actually didn’t realize that Mesh To Metahuman would take a Metahuman mesh and use it exactly rather than making a smoothed approximation. This would greatly simplify the workflow in the link above and eliminate the need for a paid plug-in. However, I haven’t been able to get that to work, and posted here: New Mesh to MetaHuman workflow for custom characters