So after my rear wheel tires were slashed, they were brought into the shop to be replaced. Now that I finally had her back, the car feels like it looks control or sways when going 100 kph. It just doesn't feel like I'm in 100% in control.

I've been reading online that it could be that it needs alignment, or it could be tire pressure? Does it matter that the rear tires are different than the front ones?

 

Did you replace them with cheap or less grippy tires? That or the wrong sizing or type of tire, for example using tires intended for a small suv or minivan instead of performance.

 

Insurance replaced them. They're pretty grippy.

 

Here are some things to check:
-Tire pressure
-Alignment (probably your problem)
-Wheel bearings
-LCA bushing went out

 

The front should have the same tires on the front, same size and same spec. This also applies to the rear. never mix tires on the same axle. If you're encountering problems then i agree with BMurray, get all of the above checked out, one of which undoubtedly will be your problem.