This is a tl;dr version of:
https://esports.exposed/ion/best-islands-of-nyne-settings/

This guide is as the game itself in work in progress, so check back regularly for updates and changes.

Still working for Patch #3. And some additional words:

The first patch is out and some things changed. I contacted the developers days ago, not only to of course share the success of this guide, but also to draw their attention to some exploitable commands. This now resulted in some limitations, which are overall a good thing, the sad part is some commands are getting forced/ignored even though just limiting some of them would've been the better way.

The config (in its new version) still has it's right to exist. Especially on lower-end systems, but also on medium end systems, you should still experience significantly better frame times and overall higher FPS, which result in an overall smoother game experience.

Also, this is not a config for you, if:

• you have that mega-super high-end system you always brag about
  
• you have a problem with overall "♥♥♥♥♥♥♥♥ graphics"
  
• you have a problem with "popping leaves" or the like
  
• you expect 24/7 support - I'm and other Discord members (https://discord.gg/ysr2XA6) are still happy to help, just don't expect an answer after 5 minutes.
  
• you don't understand that you might have a different experience with this config. I "only" have two systems to benchmark on, it might be different on your specific system. That doesn't mean that this config can't help other people.

• Download the newst version here:
  https://esports.exposed/ion/best-islands-of-nyne-settings/#high-fps-config
  
• Replace the existing Engine.ini in \Users\YOURUSERNAME\AppData\Local\IONBranch\Saved\Config\WindowsClient
  
• Make it read-only
  
• Always check back for updated versions.

The only launch option I know of which works is "-sm4" (or -d3d10 which does the same.)

-sm4 makes the game use an older shader model, which usually will indeed improve your fps, you might experience graphic glitches or other problems. Just see if it works out for you.

All the other options like

• -malloc=system
  
• -maxMem
  
• -refresh
  
• -USEALLAVAILABLECORES
  ....

either don't work at all (aren't even part of the Engine or Game) or won't give you any improvements.

The most in-game settings are quite self-explanatory and if you're all about max framerates and smooth gameplay, you usually want all of them set to LOW.

Noteworthy Settings:

Render Scale
Render Scale is something you might know better as Resolution Scaling. But do you know what it does?
Render Scale determines the resolution your game will render in and is a percentage value. If set to 100, your game will render in the resolution you set it to. If you set it lower though, it will render in a lower resolution.

Example:
Resolution set at 1920x1080, Render Scale set at 80.
Result: Your game will render in 1536 x 684 and not 1920 x 1080!

No, the devs know about the guide. It's not endorsed or supported by them, but also not cheating or even a bannable offense. Developers have always the possibility to make the game just ignore those changes to a user's configuration files.

Editing config files in your user folder is not the same as editing game files. The later, editing game files, like for example local map files, is obviously forbidden. That has nothing to do with this guide though.