If you want to make the game more realistic then Realistic Mobs Mod will help you with this. With this, many mobs become a size that is close to real life. For example, spiders will be reduced by several times and will be tiny. You will have to work hard to kill it. At the same time all the characteristics remain the same.
Realistic Mobs Mod for MCPE 0.16 changes 15 mobs but some of them will remain the same. The Creator did not change some mobs because he was not sure of the correctness of their size in real life, such as a golem or enderman.