Does it wear there tires unusually? Any downsides in that respect?
I would it think it depends on how and where you drive the car.
With the Fiesta, I think -3 front -2 rear will get the most even tire wear on hpde and probably autoX or if you do a lot of events but don't want to go to the alignment shop too often.
I think -2 front -1 rear will make the most sense for mostly daily driven car. That also worked pretty good on my Fiesta, mostly stock suspension or Meister 8/6 coils with maybe 5-6 days of HPDE and 1 autoX event with my first set of Z3 tires.
Tire wear on the outside tire wasn't so great but not so bad I destroyed a set of new tires with a single track day.
Now on -3 and -0.8 to -1 rears and car drives totally acceptable, rotates well, tire wear a lot better so I save money on tire wear in the long run.
If I were to get the rear camber shims it would be to save a bit more money on increasing tire wear in the long run.
With other cars, had -2 front and -2 rear on my daily beater civic and it just wore out inside of my rear tires a lot more.
Had it switched to -2 front and -1 rear, then the rears had more even tire wear.
Couldn't really discernably tell if there was a difference in rotation or less understeer there as Im not that good a driver that I cant drive 10/10 on the streets.
Had -2 front and rear on my evo, used mostly for hpde and a bit of canyon driving, very little street driving. I wore out the outsides of the front more and rear a tad less so, even with tire pressures dialed in.
Switched to -3 front and -2 rear and got much more even tire wear. Car seemed more willing to rotate but wasn't as notable as I'd wish for.