1) What exactly is the Sunni position regarding Mu’awiayah?
Salaam alaykum wa rahmatullah,
I think a more important and insightful - perhaps even helpful - question would be this: what was Imam Hassan's (ra) position regarding Muawiya? I am no fan of Muawiya but one of the reasons why I respect him is because Imam Hassan (ra) entrusted him with the fate of the Ummah.
Consider all the things Shias make Muawiya out to be. Is that the sort of man that Imam Hassan (ra) would abdicate his "Divinely Ordained Right" to? I cannot imagine Imam Hassan (ra) vacating his position for a "purely evil" man.
2) what is the Sunni position regarding Yazid?
I cannot imagine anyone who was directly involved in killing Imam Hussain (ra), or had a hand in devising the plan, can enter Jannah. Anyone responsible for killing Imam Hussain (ra), including Yazeed, in my opinion, is scum.
However, to get you to reflect on your own, independent of the Shi'i belief that Yazeed was out to distort the religion, what does authentic history say about Yazeed? Not much! Let us agree that he was a womanizer, an alcoholic and never prayed. So what? We challenged all the Shi'i members on this forum to bring us one authentic report, from Shia or Sunni sources, which proves that Yazeed was out to destroy Islam. Not a single piece of evidence was furnished!