How to enable 'Export Smoothing Groups'?

I have created a character in Adobe Fuse CC (Preview) and sent it to Mixamo for auto rigging. Once it was compete I downloaded the character in FBX with a T-Pose. When I imported the character to Unreal Engine 4 (4.14.1) I got this error:

My project is for Mobile/Tablet - Scalable 3D or 2D - No Starter Content (Third Person) and also this happens:

119417-ue4+error+2.png

I fixed it by changing the Blend Mode to Opaque and after that I got these results:

Is it the ‘Export Smoothing Groups’ that’s doing all this and will it give me more problems further in my project ?
It’s my first time on here so I hope I addressed my problem properly… I’m very new to game development so please explain in details if you can