if I were to do #%/%(some-fn %2:x %1y ... x) would the x be bound, or will I have to repeat the %2:x

x would not be bound. You'd have to repeat %2:x, like you would with %2

The symbols don't result in bindings. They pull the values out. %:akey is pretty much translated directly into (:akey %)

Though % takes on a more unique name under the covers.

so %:x %:y assume the function is passed a map {:x 1 :y 2}

I wasn't clear on if it was just positional or doing some desructuring

Right. A number represents an index into arguments passed in. The key does a lookup in whatever argument is selected.