I used enteric coated peppermint capsules many years ago, but for constipation,not diarrhea. I noticed some minimal action in the beginning, but it quickly ended up doing nothing.
I think it's generally used to unblock constipation, so I'm not sure it'd be good in your case. However, there might be something that is soothing in the peppermint for your system, so it still might be worth trying.
Between me (who has a long history of IBS-C) and my husband (with IBS-D) I have LOTS of experience trying all sorts of interventions/remedies and troubleshooting GI issues. If you want to give some more information, I'd be happy to try to come up with some other ideas that might help.
Some info that would be helpful:
1) How frequently do you get bloating and diarrhea?
2) Do they always occur together?
3) Do you notice whether it gets better or worse depending on what you're eating?
4) Do you notice whether it gets worse if you are stressed?
5) What do you eat in the days just before/during your GI distress?
6) What have you tried already (and what were the results)?
If you can elaborate on these points, I feel confident I can come up with at least some thing (if not several things) for you try.