It seems like the edges of your 3D objects have a light gradient effect. It looks great! How did you set it up?
I tried out a bunch of Blender themes (v 2.81 and 2.91), but I couldn't quite get it...
Looks like he has Cavity enabled. You can enable this from the shading menu dropdown under Options> Cavity, and then tinker with the settings to get a look you like. It's really helpful!
