Sorry, I had to leave yesterday before I could reply to your actual question (your three options).
I’d probably choose option 2 …for now. If you can get a twig of Pristine, rather than buying/planting a third tree , I’d do that.
Eventually, your B118 alone, will produce more early apples than you can use, but you can await & deal with that when it happens (re-grafting, possibly removing one of the trees etc). But for the first few years of fruiting, I think your existing two trees will give you about the right amount of early apples.
I’m pretty sure that you’ll eventually want only one early apple tree (B118’s get big unless you do hard pruning) but if you have the space and since they’re already planted, I’d keep both for a few years & re-graft branches, as the trees and your family’s appetite changes.
Just one more thought: Fireblight has been a terrible problem with Yellow Transparent for me Yellow Transparent seems to be as susceptible as Clapp’s or Bartlett.pears. Yellow transparent isn’t a reliable tree (for me) to graft anything else to. Even if the other variety (eg Pristine) is blight resistant (which it is, in my experience) Fireblight can still attack one of the remaining YT branches & travel into the main stem of the tree, killing everything. Of course, if fireblight isn’t a problem in your area, this doesn’t matter. ( If fireblight is a problem in your area, you might consider grafting Pristine to your Williams or buying that third tree .)