Editing the config

Wuzzsup

So 1st of all I'm a ESL player in IW4 and there have always been bitching because of configs and what they actually can do...
I know pretty much about the config in IW4 and what you can do with it , as long as its the normal CoD config.
Well there have been some clans that even had special "Config Developers" and what they did was in my opinion pretty insane...
There was a russian clan that had his own config , if you played with it you had no trees and grass and all that shit so it worked like a texture hack , but they did even more. I've not seen that config but pretty good mates told me about it and they got about 4k playhours IW4 so I dont guess that they talk bullshit. They also did a config with just glass or yellow walls , the yellow walls mark the walls that you could wallbang through...
I dont wanna have a unfair advantage i just wanna know how that shit works , I mean theres obviously not such a command as seta r_trees "0".
Ive read that the engine from CoD is based on the Quake engine ( Quake III/3 Arena ) so you could use quake configs that got more commands in it , could you?
But there is also more weird shit possible like seeing Barrels through walls or if you host that your teammates got the emblem of their team above their heads.
Also thought about Hex-Editing ( I really dont understand much about that one ) because you could change your FoV with it , so you dont need to use a FoV-Changer , which
is bannable in the ESL.

Thanks for reading and soz for bad english