Jeeps published numbers clear up the lift question. A base 2018 Compass Sport 4x4 will come factory equipped with 215/65 R16's, which have a diameter of 27". A base 2018 Trailhawk should come factory equipped with a set of 215/65 R17's, which have a diameter of 28". The Trailhawk tire is exactly 1 inch taller than the non-Trailhawk tire, which should lift the Compass Trailhawk by 0.5".
Jeeps published ground clearance numbers show that a base 2018 Sport 4x4 has 7.8" ground clearance, and a Trailhawk has 8.5" of clearance, which is a difference of 0.7". As 0.5" of the difference comes from the larger tires, the actual vehicle difference is 0.2", or 5 millimeters. That's the air dam.
A 225/75 R16 is going to have a diameter of 29.3", which willy fit fine in your Sport and will increase your ground clearance by over an inch. Is the IG public? I'd love to see what it looks like with those tires.