Slow sculpting on high density meshes iv'e seen people sculpt meshes around 5 mil verts with no lag whatsoever, but everytime i come close to like 1m and above the lag starts to be noticeable and soon any sculpting becomes unusable. 

Im well aware that this requires good rig, but i belive that with 32gb ram and gtx1080 i've got that covered.

Tried dyntopo and multires, seems that multires is slightly better performance wise, but it is still far from smooth on high poly counts.

using blender 2.79
but you are referring to lag when nagivating or when sculpting? dyntpo its better for having less polycount when sculpting but it affects the mesh and without a way to to delete it or undo what you done after finished the sculpt and also it works with triangules instead or quads. multires instead save this information in the modifier and makes a even subdivision in the whole mesh, but some times not necesary to have all the mesh subvided in areas that you wont sculpt, and it stays the original polycount and topology of the original low poly base mesh used. but you can use both like he does https://www.youtube.com/watch?v=Nc3cRVG3me4 also avoid to have matcaps and the outline select option checked because it will put it more slower when its very high poly.