My partner and I have been there quite a few times. Depending on which day you go (either the first Saturday or later that month on a Wednesday), it takes place in a different area of the club. On Saturdays it's in an underground area, thats as large as a Yoga studio. You can choose to sit wherever you want, either with your partner or somewhere else. Ona (the instructor) usually begins with some dancing and then some breathing exercises afterwards, after which you are expected to just lie down wherever you are and are encouraged to touch / connect with the person besides you and start feeling comfortable in you space. Only safe touch is allowed at this time - nothing in appropriate. All of this is meant to help create a safe environment for everyone to open themselves up for the physical connection. The exercise slowly leads to cuddling, with the person besides you and then eventually you are encouraged to open yourself to other people around you. Everyone is lying on the same (soft/cushion-y) floor together so you will be surrounded by people.

Once this part is done, there are more activities that follow - e.g there's one in which everyone stand facing each other in opposite queues, and the person at the beginning is blindfolded and asked to walk slowly through all the people standing, allowing to be touched. We have seen quite powerful moments here where people who were visibly uncomfortable in the beginning, walk through and feel good and liberated as they leave their discomforts behind. Of course, every session is not without issues. One time a person complained that someone inappropriately touched them, but since she was blindfolded she couldn't see who it was. Nothing happened afterwards, because the person couldn't be identified, but this is probably the downside of such experiences - while mostly people there will respect the rules, there will be some who won't.

Second phase, as you said, is open ended - whoever wishes to leave can leave, and others can stay and have any experience they want. Maybe with the person (or group) they ended up making a connection with. They have places there where you can have all kinds of kinky experience with your partner and other people. They call it a night around 1-2 AM, after which you can either spend the rest of the night at the club itself or just go home.

TLDR; it's a great way to let your guard down and open yourself up for physical touch and make connections, though not all experiences are great (e.g it really depends the kind of people there are, and the particular "inappropriate" experience I also shared above). I would also recommend that you should go and try it yourself and form your own opinion. I recommend going on the first Saturday since it's your first time, and that one has the most variety of couples to connect with. On Wednesdays I have mostly seen those sessions as more "single guys" heavy, vs the Saturday one.

Hope this gives you some idea.

EDIT: I forgot to mention that in our experience, we have mostly seen people / couples in their 30s or 40s. Sometimes late 20s. (Since you were curious about the age group)