Cool story.

I'd leave it alone until late winter / early spring, then select one scion as the main leader and snip the others off. Probably doesn't matter which one you pick, as they are all obviously healthy.

Yes, that's a good approach, although replacing individual scaffolds by grafting higher in the tree might lead to quicker harvests. It doesn't matter at this point if there are three pieces, you can begin next late winter-spring to pull two of them to a more horizontal position to be the first bearers of fruit and then remove them either gradually or quickly as the leader takes over the entire tree. Even when I do a single graft I usually get two buds that send out almost equal growth and I pull one of them near horizontal the second year.

In your case, I'm not sure it wouldn't be best just to leave them all growing upright and to cut away anything from the other two crowding the one you choose for your permanent leader.

The more leaves feeding the stub the sooner you will complete the conversion as well as close the wound.

This gives you something to work with, I hope. No hard rules in any of this but ultimately it's best to maintain a tree with a good ratio between trunk diameter and scaffold diameter. Permanent scaffolds should not be more than half the diameter of the trunk at their point of attachment to that trunk. On vigorous varieties 1/3rd is better.