World Composition - Performance problem with multiple levels

Helly guys,

recently I tried to use the world composition feature of Unreal, but I have massive problems with the performance and I can’t find any solution for this. Here are some details:

I want to create a 18x18km landscape and for this I am using world machine. The terrain is created, everything is fine and now I exported the whole map in 18x18 Tiles. Each tile is 1009x1009px and I press the import button in UE4.
The world composition is builded and my performace is extremly bad - around 5fps.

Well okay I thought, these many tiles are way to much, so I have to reduce them. Exporting the same terrain now with 2017px tiles, to have 9x9 tiles. The same - the performance is a bit better, but still around 15fps. Okay, next round - now with 4033x4033. The same. Now with 8129x8129. The same.

The best performance I have got so far, was around 50fps in the close up, but this is ridiculous low - especially with the PC I have here (2x Xeon E5-2680 + 96GB RAM + GTX 1080 Ti). The strange thing about this is, that unreal doesn’t use the full potential of the PC. 2-3% CPU and around 20% of the GPU - so there have to be something else wrong.

My ratio so far was 1m/1pixel - so I tried 10m/pixel. The same result.
Whenever I add a map to the world composition and place a landscape, the fps drops immediatly from 120+ to around 50. This can’t be right.

What is my problem here? Am I using the wrong math formular for the textures, or is something else completly wrong?

Just to get it right, this is my current approch. I don’t need exact values, so I useed the values given by epic.

1009 pixel are around 1 kilometer.
For 18 km, I need a Normal Build resolution by 18162px (+1).
My tile settings are at a resolution by 1009px and a tiles per side of 18x18.

When I want to have a 10m/1px ratio I divide the whole thing with 10 and afterwards in Unreal I use a scale of 1000
Just for example.

I hope you can help me and have a great day - thanks!

EDIT: Oh, one thing to mention.
I can’t use streaming distance, because there will be situations where I see the whole scenery. So this is no option, but I think this isn’t the problem here. Even with one single level the drop happens.

The world composition does not seem to be perfect, leading to problems such as fps reduction or AI drop. The official explanation is that more terrain components will bring huge performance consumption, so the big map needs fewer components, 8k map you can Divide them into 4x4k tiles or 16x2k tiles,Or set these in the viewport. When editing the map, only the tiles around the map are displayed. If you want to assign all the sub-levels to a certain distance, I am sorry that I am not good at English. I also hope someone can help me. Solve this problem because the big map causes the FPS to be too low

Where do i find “Strean in level automatically when camera is moved” ?