It does definitely depend on a few factors.
The most important one is probably your relationship with your Ex before the fallout/discovery of their secret identity. This is defined by a few things, the most obvious being whether you were married out of love, convenience, necessity, or on accident.
If the two of you weren't married for love, and didn't fall in love later, then the Ex won't be jealous, since there were no feelings there to begin with. (This isn't to say that they won't fear you outing them to your RO, or anyone else your close with for that matter...)
If you were in love (either married for that originally or fell in love after being married), then there's a few other things that might factor into whether or not they're jealous, and just how far that jealousy goes, example:
Raf is less likely to act on any jealousy than Lucy. Lucy is more impulsive, and more outspoken, while Raf tends to overthink his actions and is a pretty reserved and shy person to begin with. As is such, Lucy is more likely, if tensions escalate, to get in a fight with the MCs new RO, while Raf is more likely to walk away. That being said, Raf'll try to be happy, or at least appear happy, for an MC that he was in love with who has now found someone new. Lucy will hide nothing when it comes to how she feels.
It also depends, heavily, on one other aspect which serves as one of the main defining features of the MCs and Ex's relationship...
I can't really say what it is due to spoilers but let's just say that... It changes how much the Ex trusted the MC pre-divorce. Which will inevitably bleed into how they view and feel about the MC post-divorce.
That is correct! Some are heroes, some are villains, (one is... somewhere between the two) and some are just your normal, everyday Nickelport citizens.
It may come to something of that scale... (Especially with one specific person...)