What is the Best Way to Make a Low Poly Landscape?

I’ve been thinking about making an open-world low poly project, but there is one thing that baffles me. What would be the best way to make a landscape? This project would have different caves, biomes, and the sort. I originally tried to do it with Unreal Engine’s internal landscape tool, but it seems a little unwieldy for what I’m using. I could probably continue using it, but I still wonder if there would be a better way. I’m much more talented at using blender to model landscapes as opposed to using UE4’s tool, but I’m not sure what would be more efficient for my game. Would making my own landscape model in a separate modeling system be better for a low-poly game if I were up to the task, or should I continue using the landscape tool?

In terms of reference, I want my game to have a theme somewhat like this video, but with a flexibility in dark and light areas.
Thank you!

When building a landscape with the landscape tools and you put in alot of segments, it will begin to slow down the whole engine
before it even covers over a big wide area… So i don’t think the landscape tool is optimized you may have to use worldbuilder for
the landscape.