The 2-7 combo is best.
I feel very confident in my ability to control the cue ball with high outside, but trying to get short side shape on the two is extremely difficult. The only path that even works leads right to a hook behind the 7. It would take perfect direction and speed. I would be 20% at best to come up with any type of shot on the 2 ball. To make it worse, I'd then be 50/50 to shoot it up table. And even more difficult trying to get past those solids for a shot on the 3 if I had a flat angle and couldn't stun across table. I believe if I tried running those balls out that way I'd only make it past the 2 ball 1/10 tries.
The 2-7 combination I can get on 100% of the time however. I feel I could make this shot about 30% of the time. Getting a shot at the two ball isn't hard if you leave yourself an angle on the 2 ball so you naturally float towards the 9 you should come up with a shot. Whatever you leave yourself will be easy enough to get to the 3. I'd guess I could run through the balls this way 1/4.
25% > 10%. Play for the combo.
Also, in an actual game (not the ghost) there is a much better reason- you can play safe. Always a better option to play a route that doesn't lead to a hook and keeps you in the driver's seat.
When I set this shot up last night I attempted both paths around the 9 ball. Going below the 9, I managed to get a decent shot on the 2 on each of my ~4 attempts. A threat of a hook by the 7 was never close. Only once was I able to spin the cue ball with enough force to get on the 2 going topside. I either hooked myself with the 8 or overran the 2. That said, my table is slow and worn, so that drastically changes the weight and how quickly I lose the action on the CB.
Going bottom side is actually very natural, and I didn't find it difficult at all. I think I said it in my previous post, but it's just a "sewer shot" that needs a little adjustment.
Now..., I honestly didn't consider the runout when playing shape on the 2. Just focused on the question of getting on the 2 off the bottom rail. Although I was able to consistently get on the 2 by splitting the 9 / 6. Getting to the 3 after the 2 would have made for another difficult shot. ...and quite honestly, a way more difficult shot than simply getting on the 2 from the 1.
Playing the 2 / 7 combo would give the best chance to generate simplistic shape for a transistion from 2 to 3. However, I think you'd need to be very close to the long rail when shooting the combo for it to feel even remote close to comfortable.
Considering the cricumstances of actual match play vs the Ghost... I think my deep seeded hatred of combos would probably have me going bottom rail to get on the 2 in an actual match. I would of course have the option of playing safe with the 2 if I didn;t like my shape, and subsequent route to the 3. Playing the ghost however requires the runout or loss, so then I would more heavily consider the combo as the best option.