I'll be focusing more on Rob since that's what I personally had been dying to hear about. Sorry Maggie!

I'm doing my best to be neutral and true to the source, but this is based on notes, not a recording. My own thoughts in parentheses.

There was no sequel written by Terry and there were no notes.

Rob said he's a fan of Good Omens. (he seemed very sincere and believable to me)

Rob had no control over the creative process of S2 nor S3. S2 was by you know who, S3 was Amazon. He was surprised to see where they were going with S2, since it was clearly leading on to a third season.

Both Rob and Maggie have "huge NDAs hanging over both of [them]"

Maggie was supposed to be in S3 before the cuts

The character Maggie is, at least to the knowledge of her actress Maggie, not a demon, despite the theories around her bad spelling.

Rob and Terry had a conversation about the ending for Aziraphale and Crowley. Terry envisioned them in a cottage in the South Downs in bed together, possibly pre- or post coital or non coital (Rob said that he actually said that).

What Rob envisioned for the finale was Azirphale and Crowley to give up their divinity and eventually grow old together. He said that would not mean to make them human, since they would have been their old selves, notably with all their memories intact. They would grow old together in the cottage, in a village with Eric, Gabriel, Beelzebub, Nina, Maggie... doing ordinary things. He described the cottage as full of pictures of Aziraphale and Crowley in their time together, with a fridge full of magnets from countries they visited... knick-knacks from a life together. Bently parked in front of the Cottage. (Rob seemed really emotional about this). He said "Everyone gets the eternity they dreamed of." The scene would have ended with the two of them, older, in their garden, and as a callback to "To the world" they would have clinked glasses with "To the universe". (I was yelling a bit to myself at that point and contemplating a commemorative tattoo)

Rob and the Pratchett Estate had no control over anything. Rob was sad do see how agressive some people were online. He said there was no question of "signing off" on S3 - it was out of their hands completely. Certainly no veto rights

The 27 pages that were mentioned were not a letter of complaint about S3. Rob says in that case "it would have been a lot longer".

Rob says he's very happy for everyone who enjoyed S3. (Felt sincere to me - he seems like a geek who truly understands love for a work of fiction)

When S3 was cancelled, some staff had already relocated for a year to the filiming location. The fight for S3 was to get something, also considering the lower-level people scheduled to be working on the project - not for the actual content of S3. The argument that convinced amazon basically was "so much money was already spent, sets built, people hired, rent paid... might as well add a little more and have something to show for it"

Rob made the mistake to believe it when he was told that he'll get the scripts and will then be able to give input. Once the scripts arrived and he and the Pratchett Estate voiced their very direct critiques, they were compleley ignored. He read out an email as an example. (he seemed truly distressed)

This was not Terry's ending. (THIS WAS NOT TERRY'S ENDING)

(honestly, Rob seems like an absolute poppy)

The snowglobes were not a money-grab, but certainly a way to earn money for further projects, for Terry's legacy, and for charity. The snowglobes were his way to still picture original Aziraphale and Crowley exisiting. He referenced Men in Black, which was apparently watched a lot in the Pratchett household, with the universe in a marble. (that does fit for me, since the snowglobe is indeed used as a metaphor for the universe in the Good Omens novel)

he said the words "the mess that was the 90 minutes"

there will be new merch (he seems genuinly excited about merch and to just to enjoy the stuff)

he was sad about all the online attacks, mentioned Rachel Talalay as an example. (Everyone should be nicer to each other)

last year at TIC6 when he was so excited about the christmas jumpers and S3 he still believed in a good finale. This was before he had seen the scripts and understood how little his input mattered

He said he had a cunning way to circumwent the NDA and it turned out to be a sign that said "terrible writing". He showed it several times in response to content questions about the contend of S3

Josh would have had a larger story in the 6 episodes, being kidnapped etc.

He had not been aware that the fandom did not want a"human ending". (Considering what we got, I do hope most of us would have been ecstatic about the ending he described. I sounds beautiful)

Did anything make it into S3 that Rob fought for? - No, nothing made it in.

What would Terry say about S3? - Read the novel.