It depends on a number of things and there could be a number of better options than what you listed.
3 of the options you listed are likely to just lead to massive plot holes.
You really need to consider the nature of the person and why they act the way they do. If you don't you will just end up writing pure shit. People do things for a reason. Even crazy people do shit for a reason. It might not make sense to you but it does to them. The reason it makes sense to them is they usually get fixated on certain aspects and loose sight of other options and other aspects.
Young son.
Having a son could be why she is willing to do a lot of the stuff she does. I've known a lot of women that compromised their values to provide for their child. Sad in my point of view that they had to actually resort to such measures. But life. However, it does show they have a good characteristic of being willing to sacrifice for their child.
That can work rather well if the child is young and not of a working age. You also wouldn't want any content involving her looking at him in that way.
It could be why she goes into stripping, escorting, porn... or taking other shitty jobs or making other bad choices or choosing the wrong people or BF/GF to be with.
An older son college age especially a step son can give you a number of other opportunities.
Son comes home for because the father passed away. Finds out dad was broke or maybe killed because he was involved in some shit...
The point she is vulnerable, feeling distraught... he steps in as a man takes care of the funeral, has her move in with him...
Maybe after some time she starts wanting to date again, tries her luck the guys an asshole... She is emotionally hurt...
Again vulnerability...
All the while the MC is supportive, encouraging ... Helping her to explore who she is and grow... (in some of the right and wrong ways)
Another option
The example. For whatever reason they are living with each other. No father in the picture or maybe he is but he is a workaholic or just a bastard... She sees her son's changes and relationships and those encourage her to start looking for her own excitement. That could be with or without the son being directly involved with her.
You could use something like a question as how does she feel seeing her son make out with a girl.
Does she get excited because its her son?
Is it just he sex that excites her?
In short you could create a measure as to how she feels toward her own son. That way that content can simply be avoided if the person chooses or if they want to see that type of content it is simply a different answer.
Domination
If she is being corrupted that tends to say she is weak minded or not strong willed. That wouldn't work well with her dominating him.
If they are both weak it is more likely a third party is manipulating both of them in some way.
Unless your story is of her corrupting the son then her dominating him shouldn't happen.
If she is the one being corrupted it is a higher probability he will be in control unless the third party issue is in play.
Your pole
Options 2,3, and 4 are almost never going to happen. Not just that they are next to impossible to support when writing and will result in just a shitty story. Mom and son relationships are a small amount to start with. When the mom initiates it the child is usually far to young to make a game with. That's when the mom is most in control. If the child never leaves home and is a total mama's boy that's the few adult relationships. If the child leaves home and goes to school or college even while living at home it isn't likely they retain enough influence to start it rather the male initiates it.
Also if mom is going after her son she usually has mental issues and is pathetic in other ways. Not someone most readers or players want to play. This would be the woman who isn't getting enough attention at home husband cheats on her, she is to afraid to leave or cheat on him in an outside relationship. The reason she has little self confidence and doesn't feel she is attractive and that may or may not be true. Often it is.
Plain and simple you aren't going to be able to write a compelling story from those 3 perspectives that a great number of people want to play.
This also means there some serious plot holes created with 2,3, and 4
opt 2. If he is one in control he probably is has the personality to go with it meaning it would be uncharacteristic he would want to share her with others or risk getting diseases like that. He would have a personality that looks down on others. After all he's a control type. Thus why would he want filth or others touching his possessions.
opt 3. As I mentioned above if she is the one in charge then she has issues that would prevent her from going after other men. That or she wouldn't be going after her own son.
opt 4. Same problem as opt 3.
There are other plot holes besides those. These women who go after the male son. Are doing so to usually fill a void. It's that fixation that drives them down that path. They aren't going to do stuff they think would risk loosing that plan falling apart.
So if the woman is craving affection physical or otherwise she isn't going to risk it by risking hurting the feelings of the son in a way that could drive them away.
opt 4. Where you do see shit like this
Mothers that resent the child. You also see it with a lot of additional abuse. This isn't going to be a game anyone will ever want to play unless they are just some really sick fuck if this is the choice.
