You don't say what camera you have, if using an unmodded DSLR you may not need anything, but if you have an astro camera a UV-IR Cut for M42 will work well, and I assume also for the Pleiades but I have not imaged that one yet.
Any light pollution filter that is still broadband should also work. You can also enhance M42 with a Ha filter (to give HaRGB) but this isn't necessary. I've had good results just with a ZWO UV/IR Cut.
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