I have a Windows 10 laptop with Minecraft Windows 10 Edition v1.0.4. When I play some worlds or in a Realm, Minecraft responds pretty well. But I have a Survival world that is 104.6 MB. (I am trying to get all the achievements, and I had to explore a bit to get cactus and cocoa beans.)
When I open that world, there is a lot of lag. The CPU in task manager goes near 100%. I am trying to kill the Enderdragon now and it's not that easy. I've turned down most of the video settings (except I need a little render distance so I can see which towers I have to take out).
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I've found that the laggiest - highest CPU times are when I join the world, and when I go through the Nether portal (either way) or when I go through the End portal. So, it gets high CPU when it has to render the world from scratch.
What else do you need?
From Belarc:
ASUSTeK COMPUTER INC. Q502LA 1.0
Windows 10 Home (x64) Version 1607 (build 14393.693)
2.40 gigahertz Intel Core i5-4210U
128 kilobyte primary memory cache
512 kilobyte secondary memory cache
3072 kilobyte tertiary memory cache
64-bit ready
Multi-core (2 total)
Hyper-threaded (4 total)
977.53 Gigabytes Usable Hard Drive Capacity
762.79 Gigabytes Hard Drive Free Space
8076 Megabytes Usable Installed Memory
Intel(R) HD Graphics Family [Display adapter]
Generic PnP Monitor (15.7"vis)
You'll need to provide more information. I have a world that is 380 MB, and Minecraft barely uses any CPU (and no I don't have an expensive new CPU: Intel core i7 processor from 7 years ago).