Would that be a race cape or a touring cape?
(race=jacket, touring=poncho, more or less).
A touring cape has such a big open area at the bottom that breathableness is deemed not to be necessary (though I get quite damp from sweat where it lies against my back). Mudguards are necessary.
Jackets are available in varying degrees of breatheableness. eVent and Goretex Active Shell are the most breathable fabrics (and most expensive), being not too far off as good as unproofed pertex windproofs. Note there are several other varieties of Goretex, of varying degrees of breatheability (Pro Shell, Performance Shell and Paclite, best first).
All breathable jackets are limited, in that after a while the outside of the jacket will become saturated, and the fabric won't breathe through a layer of water. After this point you'll get wet from condensation.
Most cycling items are just yellow, with only small amounts of reflectives (piping etc).
To get proper reflective, you'll have to go to
industrial workwear (probably at the lower end of Gore's breatheability range).
In summer, the other option is just to wear stuff that doesn't get too uncomfortable when it's wet, and let yourself get wet.