The point here is that you aren't permitted from casting twice at all. The only thing is that one action must be move. So when you've used this spell that allows you to carry over a bonus action to the next round, then you could in theory cast two spells (I think) and still ...
Chance. You sent me an easy question, so you get an answer. I’ll tell you what I do with spellcasting monsters. I don’t use them. I mean, I do have monsters that cast magic spells. But they aren’t spellcasters. They don’t need to be. ...