There are generally 2 aspects to filters:
First is to match a prescribed band pass containing specific wavelengths to be captured for specific purposes. This is the reason for most of the photometric systems and why there are more than one. These filters are often used in pairs or groups with their results ratio-ed to get the final data. Per another thread, you want to choose filters that tie to the research in these cases, IMO.
The second use is to provide a performance improvement not specifically worrying about the wavelengths. The CBB seems to be one of these as are narrow band filters in most cases (as weird as that sounds). I use a Sloan 'r or a long pass orange, red or long pass NIR filters for speckle.... each used for performance reasons with total disregard of the actual wavelengths. The key here is to understand what the filters are doing and use them to your advantage.
So what is the CBB filter doing with EXOs? If you look at the filter response, the CBB cuts the blue and is being applied to all star types. Blue scatters more than red and bends easier. Seeing improves with the square of the wavelength, that is 800nm has 1/4 the seeing distortion of 400nm. So clipping the blue likely give a little better/sharper dip. The long pass v.s. a closed band pass gives as much signal as possible. If you look at the literature, folks are using everything from photometric filters and long pass filters from the NIR to none. I'll ask Tuesday at the NASA Exo-Planet Watch meeting, but suspect there isn't a preference.
My suggestion above is based on:
Yellow long pass gives the most photons while limiting the blue scatter (and halo in some refractors). #8 lets in the most, #12 looks close to the CBB and #15 cuts a little more as seeing degrades, #21 for
further seeing reduction. These LP filters are quite inexpensive. If Light Pollution is bad, choose filters that cut the pollution bands or use bands that omit them. I hate to say it this way, but there aren't any
rules here :-)