1. I have a few thousand objects per layout - most of which are static. However, instead of creating 10 sprites for each individual object, I usually create 1 sprite and add 10 frames to a single animation and turn the speed to 0. Will this negate the effect of the Render Cells?
The engine only ticks sprites with more than animation frame *and* a nonzero animation speed. So if the speed is 0 it will still be a static object. Note if you change the animation speed, it will start ticking it again.
[quote:36llqibo]2. Some of my static objects have minor angle sine behaviors (nothing that would take it out of a cell, I wouldn't think). Will sprites with behaviors like that be problematic?
Moving objects becomes more expensive on render cell layers, so for ideal performance they should go on a non-render-cell layer. However if there are only a very few objects it probably doesn't matter.
[quote:36llqibo]3. By turning it on in my most "static object" layers, I still don't see any difference in CPU. Does that mean they were never really an issue to begin with? Or am I missing something?
You should check on a low-end system or mobile device to see if there's any measurable difference. If there's no measurable difference, either you don't need to use it, or you have enough moving objects to negate the performance benefit.