Lag hasn't been very severe in past versions of MCPE that I experienced, so I'm not sure if it's my phone (which is an Android ZTE GRAND X MAX +) or the game, but chunk loading takes forever now, no matter the render distance! I noticed that the slow chunk loading is most prominent when I'm in chunks that I have visited before. That, and the world generation for already existing worlds take forever for me, and time still passes when the world is generating (it'd be daytime when I last time I played, and then it'd be nighttime by the time the world generation is finished)!