The 3-5 seconds is for changing a material override on an element, if the SEO' are all cancelled then this change is instant. But have been noticing other issues when changing views, going to a floor plan with a different cut heigh seems the worst, sometimes 30s to 1min.
I know that it will never be instant on an Imac, just didn't expect it to have such a significant drop in the plan space and the 3-5s lag for basic setting changes is a bit annoying, mostly because it is instant without SEO's.
SEO's are only ever used deliberately, the base slab of a building is virtually the only object (or sometimes objects) cutting a mesh, walls are never used. But the problem seems to be rooted in inter object SEO's either discretely applied (Never holistically selecting all of this and trimming to that) or automatically via intersecting building materials, not really with any meshes (and meshes don't participate in intersections anyway). Particularly the ones between walls and roofs seem to be the problem.
Have already copied the file an deleted all SEO's and noted an improvement in performance, however when you also level all the layers intersections to 0 (so no building material intersections are computed) it also speeds up significantly. But at least you can manage that portion of the slowdown with layer combos.
AC 24 5004 AUS
iMac OSX (10.13.6) 4.2ghz i7
8gb ram/8gb vram