Completely disagree about Cap. He made his stance very clear. Governments change and he couldn't be sure that it would be the right people overseeing where they go, or that they would be allowed to act when it might be very necessary for them to at some point in the future. It just so happens that Stark was also right about them needing to be answerable to someone and take responsibility for their actions when things do go wrong. There might be some middle ground in there somewhere that would have satisfied all parties, but they didn't have time to really discuss and explore it before the situation with Bucky blows up and Cap is forced to act outside the law to try and help his friend.
I disagree with this as well honestly. Was Tony somewhat naive to just go in and trust the government? Maybe, but he also told Cap he wanted to sign it so they could work on improving the accords down the road but that they do need to be held accountable for what they do. Considering Tony is a man who's weapons killed who knows how many people, who's ego nearly got Pepper killed in Iron Man 3, and who almost destroyed the world by accidentally creating Ultron since he was literally answerable to no one it's not surprising he's started feeling this way. He's a guy carrying around a lot of guilt for the things he's done in the past and he's probably the least capable of coping with it personality wise. So when he's yet again faced with the horror of the things he's done he does his best to do what he thinks is right, but once again kind of let's his ego get away from him by thinking he's right and there is no other way forward at the time. Shortsighted surer but not a tool. He's a flawed man trying his best to make up for his mistakes and he doesn't always make the right choice. It's part of why he's such a great character.