There shouldn’t be anything in MegaLights what makes it slower when you start rotating static meshes.
If those would be meshes with WPO or skinning then you would incur extra BLAS build costs, but 10 simple meshes shouldn’t cost much.
My guess is that this is due to some legacy moveable object interaction tracking per light. Try to disable it with r.Visibility.LocalLightPrimitiveInteraction 0. It’s not needed for MegaLights, but we run out of time to handle it properly. Through this cost would also incur with VSM.
Otherwise it would be best if you would disable async compute using r.RDG.AsyncCompute 0 and then profile both cases using insights or something in order to figure out what gets more expensive.