As the poster before me pointed out, that epvpr's post is likely your best "tutorial" for FPS, just keep in mind, it'll be trial and error. Sleep is used in different places in the client as you'll see.
As far as the resolution goes, on older clients (I'm not sure on modern CO3 stuff), the supporter resolutions of 800*600 and 1024*768 is hard-coded in a lot of places within the clients Conquer.exe, so you'll need to trial and error that too.
There's some values that are for the login screen, some for after it.
You'll also need to keep in mind the GUI elements of the client, they're loaded in through "ini/GUI.ini" and "ini/GUI800X600.ini", which one's used depends on the Screenmode specified in: "GameSetUp.ini"
And there's also some GUI elements that are hard-coded, so you'll need to figure that one too.
A reference you should look at:
https://www.elitepvpers.com/forum/conquer-online-2/215781-changing-co-resolution.html