Underground scene advice

Hey I am creating an under ground level basically it will be an underground prison with a tunnel leading off it to get to the next level nothing over complicated. Just a bit of advice on the actual creation of the environment the “cave”. Would it be best to create it all as a static mesh and import then add all my meshes inside or do you think I should do it all in ue4 so by using various meshes to build to the tunnel etc by placing together a lot of large rocks
Thanks

Hi!

There are no restrictions. You may use a modular system, as in this example:

Or completely build your level in the 3D program and import it into UE4. But if you're developing a game for mobile device, you will need to find out which option gives better performance.