Hello ArcaneTheWoof,
So there are several factors that drive the resolution of shadows and lighting on models.
From the Pre UE4 :
1.) Model itself.
2.) Topology/Tessellation
3.) Smoothing
4.) Normals
5.) Light Maps
6.) UV Maps
In UE4
1.) Increase Light Resolution
2.) Enable Generate Mesh Distance Fields
I will link you to the documentation on our Wiki Page for you to study and then you can make a decision based around your project.
The first is a troubleshoot if you find yourself stuck.
The second is our official documentation on shadows,
Thanks,