You can put your hacks anywhere you want, hell even in the Steam directory if you want. Autoexec is just a name for a config, but it can be anything you want it to be. The launch command "-exec autoexec.cfg" just runs any commands in that CFG when the game launches. You don't really need it unless there are important commands you want the console to run everytime the game launches. There are no such thing as undetectable hacks, all hacks will be detected sooner or later. Check the CSGO hacks section and look for hacks that are new (etc released today) and they will likely be undetected until a few days.