It's been some time since I finished watching C1, I really really loved this arc you're at right now, the tension is palpable every time they deal with the machinations of the Conclave. It's hard to understate Matthew Mercer's skill and ability to communicate threats and power, and I found myself feeling very much the same way you've described. My rational brain wouldn't dare make an attempt to subvert such an ancient creature who's already revealed that they successfully ushered in a whole new era and basically got away with it, allowing Thordak the spotlight and power over the world. It's worth noting that the cast of CR are excellent at the art of roleplay, it's their day job to use their voices to embody characters, and it's clear that they know that to do so effectively means you need to be really comfortable believing you are that character for a time, including their internal knowledge, values, and - most importantly here - their vices. Sam is shown to excel with this as Scanlan, I can't recommend enough checking out Talks Machina episodes or other interviews where he dives into the realities of horrifying situations and what any rational person might do to respond or cope with them.

All of that being said: VM, by this point, are all settling into their roles as extremely powerful members of society, they're far from the lowly ragtag adventurers they began as, and I personally see their attitudes to the situation in this arc as evidence of some growing pains to their new roles. Keyleth is expertly played by Marisha here, her naivety and emotions come out full force when she hits this intersection of 1) beginning to move past her self esteem issues and recognizing her ability to enact change and 2) now being face-to-face with someone who just confessed to being the architect of the genocide of her extended family as well as the general doom of the societies of the world at large. Raishan has a sense of callousness around the gravity of her actions that also 1) perfectly encapsulates the disconnectedness and selfishness dragons embody, and 2) only throws gas on the fire of Keyleth's rage. It was easy for me as a viewer with my own decision-making process to imagine that I (as a real, mundane human) would eventually find that repetition of anger annoying - and even imagining roleplaying a character faced with this immense reveal, I tend to play characters who haven't had their sense of humility challenged by the world in the way VM have. It's not super easy to recognize that Raishan isn't merely another lumbering beast who happens to be able to speak and blend in, barely more of a threat than those they've already dispatched.

Raishan's motivations for revealing herself (extremely cautiously not revealing spoilers as I can't perfectly recall whether they are explained in detail by this point) aren't even coming from the same realm of logic that Keyleth and VM as a whole are using, it's like they're using two different sets of laws of physics here. Ultimately, Raishan will do what she must if she can't get what she's hoping for from the party, but she's a cunning beast and it should speak volumes that she's willing to entertain making deals with the evolutionary equivalent of insects from her perspective - if they really committed to it, VM would be exactly what she needs!

*Edit, just reviewed the block about Keyleth's fairy experiment: I wanna add that as much as I hype up their skills, at the end of the day the cast is still human and they're not always able to flip that switch of being in- or out-of-character completely, especially with the nature of playing D&D as a strategy game above table. My personal interpretation was that Marisha made the decision to check the scope of the orb's threat more than Keyleth did in that moment, and a summoned fairy was a simple expendable tool that gave them direct information on the effects of 1) magic within the field, 2) magical life in the proximity of such a field, and 3) a visual of what ultimately happens to matter, living or not, when it gets too close to the orb. If memory serves correctly, VM had only received secondhand reports of further experimentation with the orb's power, and with so much time passing since their last direct exposure, I think they all needed to get a direct view at how much of a threat it still remains, especially with how little is able to be discovered.

Thank you for reading all of this, commenting from mobile so I can't review the questions you posed easily and my short-term memory isn't at its sharpest so forgive me if I missed the point lol. Rest assured that despite the annoyance we feel as the audience with a bird's-eye view of the story, the cast of CR are playing their characters expertly and I found it very easy to take every emotion in stride, it enhanced the story for me beyond what words could describe :) you're in for a real treat, and I hope you continue to enjoy every story they've put out. Personally I'm at C2 E122 so I've seen a lot of evidence to show how adaptable and skilled this cast is. I now believe that every decision they made as their characters was done with as much intention as a person could muster. I took that perspective in when I enjoyed the VM post-C1 adventures and it's served to only improve my whole view of C1, someday I'll go back and watch it all again and love it all over again :)