I've attended a number of virtual events, and with different organizers, and I would really recommend you attend more than one, because, especially if there's no financial cost or commitment to join a certain number of sessions, the people who might drop in to any given session can vary greatly. The moderator / facilitator's skills will often impact where things go.
In my experience, most participants tend to fall into one of the following categories (my apologies for categorizing and for the naming of the types - I am bad at this and mean no offense to anyone):
1. "Classic Aspie"
These are your folks who are typically introverted, don't talk much, but can go on forever if something of interest to them is raised in discussion. They're usually there for the social interaction, and might be looking to validate their experiences and thoughts, especially for the older members who are self-identified. They may or may not be looking to make friends or connections. The moderator's main role with these participants is to gently let them know if/when they should share the floor with others.
2. "Hanging Out"
These are your folks who are just there to listen. The only time you might hear them speak is during introductions and to pass during the end of the session roundtable.
3. "Extrovert"
Like Luca, these types tend to be able to comfortable with socializing in general and already have, unlike the others, a significant friend/acquaintance/social network. They tend to show up out of curiosity, or to ask questions about something specific (like asking for workplace accommodations) and so might only show up on an itinerant basis.
4. "I Need to Talk About My Trauma"
These folk often have a lot of trauma and no friends to talk to in real life. They see the group as an opportunity to talk (rant?) about their trauma to get things off their chest so to say, and may often steer the conversation that way. Moderators need to be careful in finding the balance between letting someone share their experience and when to step in to recommend support services and to steer the conversation away. I've been in sessions that more or less devolved into an extended pity party. That's not necessarily good for anyone, especially since some topics can be triggering and bring back unwanted memories for others.
5. "Socially Awkward"
These folks are desparately looking for friends, but have no idea how to do so, and their conversations tend to be very socially inappropriate and cross boundaries, even in an autistic group. Their manner of conversation can be akin to an interrogation. Sometimes things get really awkward as they're trying to engage people in the general chat and also PM'ing people directly. The moderator may have their hands full with ensuring that they don't make other participants uncomfortable. I feel really bad as these folks need help, but a chat group isn't going to be the place for that.
I'll give an example of a "Socially Awkward" type conversation where I'll call them X (and this is via PM):
X: Hi Victor! Nice to meet you. My name is X. I'm autistic. I'm 21 and I'm a student at UCSF. I'm studying physics. I live in Oakland.
V: Hi X. Nice to meet you too.
X: Where do you live?
V: I'm in the Bay Area too.
X: Where exactly?
V: Near the middle.
X: Which city?
V: (getting annoyed) San Mateo.
X: I live with my parents and my one sister. She is 25. Do you live with your parents? Do you have a brother or sister? How old are are they?
V: (really annoyed. In the meantime, in the main discussions, X is similarly trying to get one of the participants to name the exact location they're in and the moderator is having to remind them that people are free to participate as they wish and are comfortable, and if someone seems uncomfortable in answering any given question, especially in regards to their location, which is also a matter of privacy, that we should refrain from persisting and respect their privacy.)
X: (repeats questions to me)
V: (ignores)