When playing on server, the game is laggy, when receives chunk from server. Chunk sending frequency is max. 20 chunks per second, but usually it's less. every single new chunk causes some lag, on powerfull devices its less noticable. I'm sure, its MCPE bug, because in singleplayer with highest render distance its less laggy than on server with average view distance.
(tested on servers without players, entities, blockentities, and in normal worlds)