Why did I go with KYB shocks? I did a research and only found 3 brands that list shocks for the 2017 Legacy : Subaru, KYB and Monroe.
The OEM shocks were still good, riding and handling is a bit better with the KYB but I am comparing 60000milles shocks with new shocks.
As far as King spring, I sent them a question with the VIN of the car and they confirmed that the shocks were compatible, the King spring are load shocks but not lift shocks, the read ride height is within 1/2'' of the previous one.
I have owned many Subaru over the years and I did tow small trailer with many of them
I did tow up to about 2500# with my current Legacy and it dropped the rear suspension more than I like.
This is the other problem: the trailer hitch is the same model than the 2017 Outback and because of the trim of the bumper is much lower on the Outback than on the Legacy, the trailer hitch is flush with the bottom of the bumper trim on the Outback and it is about 7/8'' lower than the bottom of the bumper of the Legacy.
This is not a problem on the Outback because they have a 2¾" suspension lift and bigger tires but on the Legacy, the departure angle is fairly low on the stock car with it's long rear overhand. With the trailer hitch, I am getting 13.5°
This is why I installed stiffer springs and I will also cut and lift the trailer hitch to try to help.
I used to have a 2000 Impreza wagon, I put 2 x motorcycle on a heavy 4 x 8 trailer and drove over 1000 miles to go to the Dragon Tail. The 2017 Legacy is a much better towing vehicle and surprisingly more fuel efficient than the 2000 Impreza and with the gas price increasing, I want to keep the Legacy