As I understood correctly the the Opsgenie integration for Check (2nd row on the screen) is is using API v1.
But plugin within Checkmk is for API v2.
We tested in the past as well scrip from Opsgenie (https://raw.githubusercontent.com/opsgenie/opsgenie-integration/master/check_mk/opsgenie). I was not satisfied 
Is it works with Checkmk v2? I guess I tested it as well without successful.
Eventually what is better way to send notification to Opsgenie from Checkmk v2? Your hints or experience.
https://support.atlassian.com/opsgenie/docs/integrate-opsgenie-with-checkmk/
or
https://docs.checkmk.com/latest/en/notifications_opsgenie.html
At that moment I am satisfied with 1.6.0p22, but we are thinking about update to v2. Therefore I made some tests.