There are some tweakables in setup.ini, which can improve performance or quality, but they canno´nt be tweaked in editor.
reflectionrendersize=512 <<< This sets resolution for water reflections. It was present in early FPS Creator Reloaded betas via Water reflection slider, however it is not active anymore. In editor there should be a slider affecting it and values must be multiples by 2
dividetexturesize=1 <<< This affects resolution of all textures. I don´t know if it does requie restart for applying it, but if it doesn´t need it, in editor should be a dropbox with [1 = native], [2 = 2x2 smaller], [4 = 4x4 smaller], [8 = 8x8 smaller]... This will allow play games with systems with low VRAM or RAM

Now another settings:
Sky <<< This will control if the sky is animated, static or disabled. Disabled sky can be used in isometric or top-down games, while disabling sky animations will improve performance slightly on Low-end PCs.
Animated objects <<< This will control animations of non-gameplay objects like trees, windmills... From what I heard, animated trees have big performance impact. On/Off in editor.
Unimportant objects <<< This setting will impact rendering of some unimportant objects like decals, blood splatters, background objects. bushes... Ofcourse it should not be used for gameplay important objects. This setting should be also flag in entity properties. On/Off in editor.
HIGH entity shader quality <<< It should be same as MEDIUM, except for three differences. on HIGH entity shader entities receive shadows and specular and illumination map is enabled. This should incerease speed particulary at complex levels at comprarison with HIGHEST entity shader but with better quality when compared with MEDIUM.

Now to the big one:
In standalone games, as you know, there are only theree very basic graphical settings, that affects only shaders. Not only that is´nt enought in most cases, but it also can create graphical glitches, like lights are not rendered on "Lowest", making games possibly unplayable on that preset. I also noticed that there are five presets in default titlesbank. So best way how to solve it is adding all five presets in standalone games.
Not only that, but in test game mode there should be Preset tweaker, where game makers can tweak settings fo those presets to their liking. And I don´t mean only shaders, but also any setting in editor that have performance impact + those metioned.
Why in test mode, you should ask? Because in test mode, you can see, how the changes are impacting graphic and playability of game. Preferably game creator should be able to tweak those for every level, becase indoors level probably doesn't need Lightrays.

This shoud improve performance, graphic and scalability of engine and games made with it, which is good for all.
Many gamers complained about poor performance while running GameGuru standalone games, including those, that are released on Steam for money.

In your standalone folder, you will find a SETUP.INI which contains a section looking like this:

[GAMEMENUOPTIONS]
graphicslowterrain=lowest
graphicslowentity=lowest
graphicslowgrass=lowest
graphicsmediumterrain=medium
graphicsmediumentity=medium
graphicsmediumgrass=medium
graphicshighterrain=high
graphicshighentity=highest
graphicshighgrass=high

If your game relies on dynamic lights, you can change the lowest settings to medium and save the SETUP.INI changes. Next time you select LOW in the standalone game, internally it will select medium shader modes.

Currently, the only way to see changes in SETUP.INI apply to the editor is to restart GameGuru. There are currently no plans to add SETUP.INI changes from within the editor, but happy to hear if more users would like to see this, and if so, I can add it to the voting board.

If you want to see, what i meant, play free GameGuru game called Shoota-Man 2
http://www.moddb.com/games/shoota-man-2/downloads/shoota-man-ii-demo
The game instructions tells you, that blue lights meant that door doen´t need key. However, on Lowest, there are no lights, rendering game unplayable.

And do you plan adding ohther thing that I metioned?
I mean those thing won't take much time and can improve performance and scalability, so GameGuru standalone games will perform well at most PCs, even modern Intel HD GPUs for example.
In my opinon, basic performance tweaks and bugfixes should be prefered than new features (Construction Kit).

And if you want to play GameGuru game, that really screams for proper graphic setting, play Verge: The Lost Chapter. You can find it dirt cheap, when you look around. Permanently enabled DOF and Lightrays murdering performance, complete darkness on Lowest preset... For me, it runs at 20-30 FPS on Medium. And yes, I know that the game was built before GameGuru patch 1.1 was around, which bring huge performance boos, but still.

@Lee

I made a bugreport about these GAMEMENUOPTIONS in setup.ini.
For me this does not work. No Medium terrain if i setup graphicshighterrain=high to graphicshighterrain=medium in standalone game.

https://forum.game-guru.com/thread/215238

Grts
Anubis