the iframe one is the right one to use...

not sure about the breakpoints, sorry - I've never used responsiveIframe myself as we have our own version - https://github.com/cgkineo/adapt-iframe - which we use, although haven't had any need to use it for some time. It isn't set up for the authoring tool either but doesn't look like it would be too hard to do since it only requires 4 properties to configure it.