Oceanpayment payment extension is a regular extension.It works well with default opencart structure .It should work with other checkout solutions like quickcheckout,onecheckout ,supercheckout though not tested and if needed it could be made compatible with custom checkout extensions with extra fees . Payment extensions does not interfere with checkout therefore conflicts should not occur at first place.

Extension is just drop and use extension made by shambhal who holds maximum reviews on freelancer.com