New to Unreal, looking for the fastest terrain solution

Greetings,

I am new to Unreal Engine. I mostly spent my gamedev in Unity for the past 3 years, all of them are 2D games. Now I am starting a team with my friends building a bigger project. I have a few question about terrain generation. I am looking for the easiest solution to build a huge terrain. I have found a few suitable solution and would like to ask opinion on these options:

  1. Unreal + Brushify Plugins
  2. World Creator
  3. World Machine
  4. Gaea
  5. We’re considering Houdini, but the learning curve is probably too much for us.
    None of my team have experience in creating 3D terrain. We’re programmers with little to no experience in creating 3D objects. We’re looking for the most straightforward all-in-one solution to create a huge game-ready terrain with its natural objects (stones, trees, river) and material. We do have a few budget but not that flexible. Can someone help us with advise/recommendation/information?

Thank you.

PS: Sorry if my English is a little bit messy.