I’d actually expect similar performance here no matter what kind of actor you are moving around (sprites, static meshes, etc…) and doubt it is sprite-specific; 35k actors is a lot. However, I’d be thinking more on order of a few seconds to move that many actors in editor, not something like minutes, and wouldn’t expect an ongoing FPS hit after you’ve finished moving things.
One other tool that is useful is that you can stream in levels with a transform offset (which is especially useful when procedurally generating levels from sublevel ‘tiles’ that you might load multiple copies of at different locations), but you shouldn’t be forced to use that for your use case.