Just did, Ryzen 5 2400g with integrated graphics, navigation is smooth as butter, sculpt stroke is lagging at around 5 million polygons. Meaning, the problem is the mesh deformation, not the drawing.
Try same thing with good OpenGL performance GPU.
I am use Intel i5 2500K and Radeon RX 570. For 6.5 million polygons and no lagging.
For 10.5 million polygons, no lag. Only if I use Symmetry or Clay brush, then a little bit lag.
Just to note, Blender’s sculpt mode performance is a lot lower than it could be (as the performance patches on the dev. site can attest to).
Speaking of those patches, what is the status of them? It was reported on the mailing list that the BF has a dedicated infrastructure guy now, so Brecht and Sergey should have a lot more time for dev work.