I have 2 possible recommendations for the config.
1) Maybe move info about dxlevel launch options to where the mat_dxlevel options are and specify that you need both to effectively change the dxlevel. It seems kind of confusing how it is at the moment. I.E: Someone may just change to the mat_dxlevel 90 option and not realize they need to add and then remove the dxlevel launch option to completely change over.
2) Maybe have the exec custom uncommented by default? I think it would be much nicer for people updating the config to be able to just copy paste/drag drop and not worry about having to change it every time. It isn't particularly difficult to change it, but just a bit nicer not to have to. That or maybe having autoexec removed and just having people execute themselves in their own autoexec? IDK, I just feel that it's easier to maintain for users that way.