The tilt of the window can be adjusted by the foam stoppers that bolt into the door and push against the window. That is how you can adjust how tight of a fit the window is when closed, which obviously you’ll want it as tight as possible. Other than that, the regulator regulates how high and how low the window can roll up or down so just bolt the window to the regulator and you’re good to go
You have two options. Either find a window regulator for an early year c4, or find the later one for C4’s like I did and drill at the bottom of the door to make the updated window regulator fit. 👍🏻