@schoening For (1), if you're constantly resizing the stage every frame you'll probably incur some GC. It's better to test this with your expected stage size and check how badly it hits GC. The last time I tried that in Pixi v3, it was more effective to perform manual frustrum culling but v4 may have improved this. I think there is also a way to hide sprites but leave them attached to the stage (i.e. if you plan to display it again), so you could just hide/show sprites and only remove them after you don't plan on showing them again. You'd have to test each approach to check which one is faster for your case.
For (3), swapping textures is generally expensive if you have to reupload it to the GPU and it will depend on the size of the texture. I don't know whether Pixi v4 optimizes this (i.e. leaving unused textures on the GPU as long as it can to avoid reuploading them). I recommend creating a test case for this too.