Thanks for your opinions.
Smooth animation preview in viewports depends of quantity of polygones
in your scene and hardware acceleration power of your graphic card of
course. Also it depends of stack of modifiers of animated objects.
More complicated stack requires additional time for mathematic
calculations, so it depends of your CPU and memory "power" as well.
You know, most general rule for comfortable work in 3d packages is to
keep in stack only necessary modifiers or collapse it to mesh (poly)
if it is possible. And last nice thing to remember is that max
degrades motion in viewports. You may edit default settings to more
accurate but it may require more powerful computer.
Regards.
swift.