Entities tend to cause a lot of lag in bedrock, even with the optimization updates it is getting. I have a good phone with 3 GB ram and yet, entities can cause fps drops(it even lags in my old tablet that is now broken with 8 GB of RAM sometimes.).

Entities causes way more fps drops than it used to in 1.12 and below. Back then, my device runs at around 50+ fps and now, it seems to drop down to below 30. I think this could be fixed by adding an option to allow the game to use more RAM if needed, or adds RAM usage cap that can be changed in the settings.

Java edition, which is suppose to be less performant, runs at around 60 fps in my 10+ year old laptop even without performance mods.