Information from:
https://esports.exposed/fractured-lands/fractured-lands-best-settings-fps-boost/
Check it out for more optimization & setting tips for Fractured Lands.

Even though the game seem to have a unlock FPS option now, it doesn't work or might at least be bugged for some.

Here is how to unlock the 62 FPS lock by hand:

Add the following two lines to the Engine.ini file, which you find in \Users\YOURUSERNAME\AppData\Local\FracturedLands\Saved\Config\WindowsClient\.

[/script/engine.engine]
bSmoothFrameRate=False

Right now Fractured Lands only offers 3 different resolutions:
1920 x 1080, 1280 x 720, 1024 x 768

But, you can change the resolution via launch option or config. It is kind of bugged though.

So if you want to change the resolution only to just lower it and gain more FPS, use Resolution Scaling instead. Here is how: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=1407614166

If you need to play on a specific resolution though, the easiest way is to force it via launch options.

• Go into the games properties in Steam -> Set launch options
  
• Add the following launch options: -ResX=1600 -ResY=900 (Feel free to change the resolution to the one you want, in this case it would be 1600 x 900)
  
• Now it get's to the part where it's buggy. As soon as you start the game, you won't see the change. You'll have to press ALT + ENTER two times to go into window mode and back into fullscreen, to see the change in effect.