If I removed my stolen I phone X device from associates device list with Apple ID can affect find my iPhone ?

Don't remove the stolen phone from your device list. If you remove it, Find-My-iPhone, Lost Mode, Erase, and Activation Lock will all be gone, so the thief ill have full use of the phone. If the phone is stolen, not just lost, you will never get it back, so leave it on your device list and use the Erase command. This will make it useless for the thief.

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

If you used Lost mode to display a contact number, you may receive a message saying the phone is found, and asking you to go to a website and login. This is just the thief trying to get your iCloud password.