My understanding has evolved slightly. I do not advise oat bran during phase 1! It can be added when all symptoms are gone or nearly gone. Also, if you have SIBO, avoid oat bran entirely.
Essential oils: I now prefer clove oil and cinnamon bark oil for treating dysbiosis (candida and/or SIBO). There is nothing wrong with peppermint oil. I just prefer clove and cinnamon bark now.
I don't remember talking about Dr. Usman's cleanup treatment but it should not cause problems. I don't know how essential that particular regimen is but it won't cause harm.