Welcome.
This is all very hard.
I think that you have a right to be comfortable in your own house and if your son is engaging in behavior that makes you uncomfortable you have every right and even the obligation to set limits within your home. He or any other person can engage in a spectrum of behaviors legal or not wherever they want, but they can't do it in my home.
There is a gray area if our children have tenant's rights. I am careful to not obligate myself with my own son, who I do not completely trust.
You are his mother. You are not a treatment center. If your son does not want to seek treatment, and he is in distress, with this, too, I think you have a right to ask him to leave. I have always felt with my own son to allow him free rein to not seek treatment, in my home, is to enable him.
All of this is not easy. Because when we set limits with our children we cut open our own heart. I am the one who bleeds most.
I am not saying that your son does not deserve privacy and autonomy about his private, sexual behavior. But you have an equal right to be comfortable in your home.
I think you also have a vote about the vaping in your home, and hygiene issues.
The way I try to handle all of this is to speak the truth. (I try to stay calm but I don't necessarily succeed.)
I am assuming you went into his room and found the concerning stuff, while cleaning up. (As opposed to searching his stuff.) The thing is this: the horse is already out of the barn. You can't un see what you saw. By not saying anything, it's kind of a lie. You are his mother. If all of this is going on, he's living a secret life. This alone could be causing depression and distress. You don't have to condemn him. You can support him. Not this behavior, but his extremely difficult position. He must be filled with self-hatred and shame.
I was reading about sexual proclivities. People don't choose them, they discover them. The thinking now is that the origin is pre-natal!! Before birth!! Your son must be so confused. I feel such compassion for him.
You can't have a vote about what he does, but you can choose how you respond. It would take courage on your part to let him know that you know. But from my way of thinking there is NO 100 percent GOOD way to deal with this. Every option is complex and indeterminate.
I would try to tell him the truth. That you discovered the stuff. I would also tell him about the vaping. I would tell him about the hygiene and find ways to support him to change. I would tell him you need this to be dealt with. That you're uncomfortable. He sounds like a kind and caring person. A good person.
About the clothes, and S and M toys, I would tell him about your concern and even your discomfort. He's not stupid. He knows who you are. Being honest is not to condemn him. All you are saying is you don't want it in the house. (You can't stop him living the private life he needs to live.) But I don't think it's wrong to have a response to it, and to have a voice.
I am an older woman. I don't judge anybody. But for reasons involving my personal history I feel very uncomfortable with unconventional sexual behavior. I am not conventional in any other way. I would have a very hard time with this in my face. Your son either exercised poor judgment bringing this stuff home, or he wanted you to find out. Either way, I think it would be a mistake to NOT SEE the elephant in the room. I think he wants you to know. He may need your help.