All the investors have stated that they are accredited. The vast majority of the investors have also made several angel investments.
You should verify that every investor you raise money from is accredited, whether or not you use AngelList. And you should treat each investor you meet on AngelList as if you just met them on the street. We give you information about each investor and display the source of that information, but we don't claim that they're good people.
You can message anyone you're connected to or who follows your startup. You can also message anyone who requests an intro to your startup.
You can also ask people on your team to forward your messages to their connections. And the AngelList team may also give you permission to message certain people.
Finally, you can message anyone who messages you first.