2Mbps would be less than 720P, I believe.
I'm not sure there's any way to tell, specifically because of the way adaptive streaming works.. If the word "1080P" or "720P" was burnt into the video you were watching, maybe you could tell, but your Roku only knows what resolution you're at, not what quality of video that streams to your box.
Not only that, but different quality of encoding can yield different results.. Sometimes a 720P Amazon title will look better than an identical 720P Netflix title that was encoded poorly, or vice-versa.
Someone can correct me if I'm wrong, and I could be very wrong on this
Yeah, I got some Rokus.
https://youtu.be/d1CSEeqWl10