This is just my take, so I'm not saying that it's 100% correct.
I believe the main difference has to do with authority. The RCC ascribes the authority of it's teaching to the Scriptures and tradition and also the pope.
The Protestant Church protested about RCC's authority, claiming that the Church shouldn't be structured in that way. They believe in "Solar Scripture", so it seems to be about authority in my humble view.
Salvation is possible in both, because both confess that Christ is Lord.
We should treat each other, as we would like to be treated. You know the, do onto others as thou would's have them do onto ye