I use the 450D with the Optolong L-Pro for most kinds of deep-space RGB. This does not mess up the colors a lot but improves the visibility and contrast. My favorite for that camera.
I do also have the Astronomic CLS-CCD, which filters out even more light-pollution, but gives a kind of strong red level to the image.
Regarding narrowband, my favorite is the Astronomic Ha 12nm. Works really good in oder to detail out the structure of many nebulae like Heart Nebula, Orion Nebula or North America Nebula.
All 3 filters are clip-in filters for the Canon. Just make sure to get the „new“ Optolong L-Pro. This has the 2 noses for clipping it into to the cam. The „old one“ was kind of stiff and tended to bend itself on putting it in.