That is awesome, @GSCUprising! I can not wait to see how it goes for you.

Writing groups can be very eclectic indeed. I used to be a library Volunteer and facilitate a group myself, and there was a big poetry influence to it, not much prose altogether. It depends on what the group is actually for - since our libraries run social objectives of getting people out and about, and they're listening out for if folks have trouble (when they chat during the break) so they can signpost them to help.

It's social first, with the work coming second. This is good if you're finding your feet. Feedback however can be...an bit hit and miss, as no-one wants to critique someone else's work. You'll need an incisive group lead or a handful of folks that want to get better, and not just present. It's a tall ask for people who come for a brew and maybe listen to each other talk. Group discipline is loose, but that's the point, but it's comfortable and non-confrontational.

That's a big plus in certain circumstances.

That's not to knock what goes on, nor anyone's talent, but that's generally what I have observed, so salt to taste.

I have also attended dedicated writing groups.

These have a completely different flavour to them. The focus is on disciplined production of work, (although never forced, but there is sometimes a push for contributions) and critique of that work. The table will read sequentially, listening attentively, and all will comment on it, giving good and bad. There's a tendency in the writer's groups to actually find folks who want to move on and develop, and the crowd will push (if they're good, and you're lucky to get editors in the group).

Again, take with salt.

That's not to say you can't push that further in a library group - but the problem is the library group has different objectives and sometimes hands get tied with what you want to do, but you need to get people in the chain engaged.

On presenting in these groups:

In the library, as you have encountered, folks aren't so bold and braying as those of us who read well, but don't let that make you a shrinking violet so you don't outshine them. Offer to read their stuff sometimes if they can't or don't fancy it, or better yet, if they ask you to, it's a compliment. Sometimes they want to hear the words they've written read powerfully, and well. Obviously it depends on your 'audience' (and you have the advantage of knowing an audience well) so do your thing, and read the room.

Sometimes your library groups are not competent or comfortable readers and their diction is difficult, but that's not their fault, I make no claims it is. People are how they are. You may be able to encourage them with your own presentation. They might be intimidated at first, but you might be surprised what you inspire. A solid reader in a group can make all the difference, and entertaining in a social setting is bread-and-butter work for those library groups.

You know what you're doing. Your voice is not on the airwaves - it's just in print, now.

Presenting to a writing group is very different. You will have shy folks, yes, but you will also have very competent readers who will complement you in presentation, and won't be afraid to put their oar in afterwards, so you might feel you're up against it! I did, but then again I'm no good at voices.

On that subject, doing voices can certainly enhance your storytelling. Audiobooks are all the rage amongst these young whippersnappers, and it can really engross them in the world you're constructing, so I would suggest (again, this is just me, take it or bail it), that the library setting is far better for this. The writing group is not interested in your storytelling - it's interested in your skill and craft. Voices can distract from what they're listening to, and editors, if present, listen differently to other authors. Use inflection, by all means, drive the sharp edge on a curse, but don't alter the voice.

If you've written the line correctly, it won't matter if you're a man reading a woman's part. It's not a script - it's a book - and the reader's voice reads in their voice, not any other, and the character will speak.

My tuppence - and good luck! You're doing something great!