For the actual mechanics of multi-player, does everyone get the same cutscenes, or everyone gets a different cutscene that is the same length, etc? Is there not enough text that different reading speeds matter?

In the single player campaign of Dragon Commander, described in various posts / interviews and shown in videos, diplomacy is based on propositions or requests that are made by your princess or advisers. You can make an immediate decision, or you can go talk to everyone to see how they feel about the issue, then make a decision based on the issue or on who you want to gain favour from.
In multi-player, this could mean one player sits around doing nothing for 10 minutes while the other is talking to everyone.

No, I have not played Total War. I tried Warcraft for a minute 15 years ago when my brother bought it, and L.E.D. Wars 5 years ago, but in a few tries couldn't last longer than a couple minutes.