I just installed a NEP throttle lock and I have a question
when installed, should the throttle release all by itself, should I need to use my hand to turn the throttle back when the lock is not latched? Not that it is difficult but just want to make sure the thing is installed correct.

When unlatched, the throttle should work just as it normally does. When latched, it should hold but still be moveable with light effort. Note that there is often some molding flash on the inside of the holding part, and it helps to clean it up. Also it will break in after you use it a bit. Adjust it properly, then work the throttle for a minute with the lock latched.