Subjunctive works a little differently in English, so please don't assume we follow the same structures and rules. "I can't believe..." is indicative of course. :) "...they did that" is also indicative. This really happened. "...they would do that" is closer to subjunctive, and more context would tell us if the speaker is predicting their actions, or making a heneral comment about their intentions.

they both make sense, y los dos significan 'no creo que..' so I think yes..