It's much less about Ren'py itself than what you're trying to do with it. A vanilla VN made with Ren'py will run pretty well on just about any supported device. (Meaning, a device that's capable of running the minimum Android supported by Ren'py.)
Now, if you're trying to do heavy animations, play movies, etc., then you're going to have a bit more issue on very low-end devices. But basic Ren'py? No problem.