Hello, the following issue was brought to my attention by @UnixRonin (#2343):

When trying to create a secondary Overworld using the Multiworld module, this secondary Overworld always seems to pick the level-type specified in the server.properties regardless of the arguments of the command that is used to do so.
This was discovered specifically when trying to create multiple overworlds with Realistic Terrain Gen and Biomes O' Plenty.

Some of the tested scenarios:

• With the level-type set to RTG
  • With RTG installed
    • When trying to generate a normal amplified Multiworld:
      it generates what seems like a normal world*
  • Without RTG installed
    • When trying to generate a normal amplified Multiworld:
      it generates what seems like a normal world*
• With the level-type set to default
  • When trying to generate a normal amplified Multiworld:
    it generates an amplified world
  • When trying to generate a BoP Multiworld:
    it generates a normal world
• With the level-type set to BIOMESOP
  • When trying to generate a normal amplified Multiworld:
    it generates a Biomes O' Plenty world
  • When trying to generate a BoP Multiworld:
    it generates a Biomes O' Plenty world

You get the gist.
I have asked Caermaster to look at this and tell me if I made any wrong statements and if he has anything to add. (He actually did all the testing. I just delegated. :P )

Additional points of interest:

• *The RTG generator is hardcoded to only work in DIM0 (it's an RTG thing)
• The generator that is fixed in the level.dat file of the DIM0 overworld does not actually seem to influence this at all.
• This has only been tested in 1.10, so this issue has not been ruled out in any other MC version.

I honestly have no idea.
And apparently I haven't even had the time to look at my Github messages for over a month, so you might understand that I have no time to test this right now.
I'll contact Caermaster about this, though. :)

As a sidenote: It would be cool if I could start using Forge Essentials for my 1.12.2 modpack server again. :)

You can use FE on 1.12.2 now. http://ci.forgeessentials.com/job/FE-1.12.2/
Please verify if this issue is still an issue on 1.12.2

I will try to make time to test this. But I can make no promises about when I will get to it.

I hope to update my modpack in a matter of weeks, which means I should be able to test FE for MC 1.12.2 as well. :D

Oh my, I forgot to close this one! I'll leave it open for the next 2 weeks then. @Robijnvogel

Is this still an issue on 1.12.2 @Robijnvogel ?