What's best rack for 2 Revo 13s on 2015 Subie Outback?

My 2012 Revo's come in at 60 lb each I believe. Subie factory rack may be rated for 150 lb.

Can you fit two boats on the wagon? Are the Subie crossbars safe?

Can one trust the factory rig and just add Thule or Yakima j-holders and run bow and stern lines for safety?

Do molded pads help cradle boats and assist hard points handling the load? (Long hauls)

Are side lifts or roller rigs a plus?

Answers in bold.
For the weight rating your manufacturer claims, I think you'll be ok. My car didn't come with racks or cross bars. I carry two Revos on my Thule racks: One is on J-racks, the other is upside-down (keel up) on the crossbars.

I fitted longer bars to accommodate the extra width of an Adventure and an Oasis so I am sure you can do it with 2 Revos (with or without longer bars)

I always transport my kayaks right-side-up and stern first in cradles because I find that it is easier to load them into the cradles than having to upend them onto the bars plus you can leave all sorts of stuff on the kayak AND store stuff inside and even in the parcel trays which makes it much faster to get set up for/from traveling at both ends of a journey.

FWIW I put inside the kayaks my paddles (works with an Adventure), fishing rods & gear, clothing, daggerbards, masts (again - these can be squeezed into an Adventure), sails and anything else that can go inside the yak. I store the carts on the parcel tray under the bungee and I leave the seats in place but folded flat to reduce wind resistance. I load all this stuff after the kayaks are on the cradles (otherwise they'd be a whole lot heavier than they already are!). Sometimes I have even put the mirage drives into the slots for transport (with the bungee to hold the fins up) - just put the kayak on the car then lift the front up off the cradle and insert the drive before strapping things down - and reverse at the other end. Loading the kayaks up this way really helps reduce the amount of car storage space taken up with kayaking gear if you already have enough other stuff to go in the car.