Generally, leveling kits are for trucks and SUVs that have a lot of rake (stinkbug look). The vehicles are build that way so that when they're loaded in the back/bed they're still level. So when "leveled" with a leveling kit, if you load up your bed, you now have a saggy-but look. This is going off-topic and IMO, but if you level your truck and don't put airbags in the back to keep it level when loaded, you're doing it wrong.
Anyway, with our cars, they're pretty level to begin with, so I think you'd want to lift both ends equally. Some lift kits for Subarus offer more lift in the rear for the same load carrying help like trucks come with (only actually more load-carrying ability if lifted with stiffer springs though. If just taller spacers in the back, then it's just so it's still level when loaded).
The budget lifts from ADF for some subies lift 1.5" front and 1" rear and say they reduce the rake of the car that way, but I think that would look "saggy-butt" and it's really just that 1" lets you lift the back without needing subframe spacers (which is also debated for newer subies).

TL;DR
Lifting only the front ("leveling") is not a thing for Subarus. Lift both ends equally.

 

I was chatting with a coilover maker, and they way they recommend setting up coilovers (The kind you can adjust rideheight) is start with a level vehicle with zero load, which can be checked at the pinch welds. If you want, you can measure the distance to the fender once it's set. Then load the vehicle with the weight you would typically carry. For me, it's a bunch of scuba gear, and then take another measurement to see how far the car drooped. The take the difference, divide by half and add that to the rear lift.

Of course, this is talking about the more expensive option, but you get a lot more control for your ride height and you don't have to deal with spacers, so you have more travel available.