The story arc is indeed very similar. You could run whatever you run as the second as a follow-up investigation. I'd recommend using UB as the first because of the WEALTH of handout material (you don't see lovingly created 50+-page conspiracy memos as a handout every day), and adapting the second adventure as a follow-up to the conclusion of bug city, where the runners find out about project hope and the potential bug army there. Bonus points if you bring in Karen King (Seattle's long-serving ex-Marine Ares rep) as the corporate help throughout the campaign and overall trusted corporate person of the group (Ares could be brought in through the plot of A Plague of Demons already), and make your players culpable for Damien Knight's Weyland-Yutani project.
I'll put a campaign sketch in spoilers, since it will contain spoilers. You sound like you're the GM in this campaign but still.
General notes: put in a street doc with UB connections and have the UB appear as good guys and helpers for the first few adventures, until 2XS. Then they become more hostile. Have the players wonder why, but keep your cool and misdirect their inquiries.
1. Module: a Plague of DemonsYou need a player who is willing to sacrifice their character for the camapign and unwilling to tell the PCs beforehand. I'll refer to this character as Lynx, as per the story, but the name can obviously be whatever. The character needs to be female though.
Run two, three shorties so the runners get to know each other, as a team. Then have Lynx disappear for a meet (that will go bust because Johnson primarily wanted Lynx). Lynx' player will have to mostly pause this adventure. Again, takes a cooperative player.
Hopefully the players want to find out what happened to Lynx. They'll trace her to a group of high-class Seattleites, all daughters of some rich fops, totally not Lynx' people. They call themselves Desolation Angels. Further investigation shows they try to infiltrate Knight Errant Seattle. This is 2050, so KE is far from what it is in today's setting, a hapless, greedy onlooker to Lone Star, the cop corp in town then.
Contact with Ares (KE's parent company) and evidence presented convinces Karen King that action is warranted, and the players get to take out the Desolation Angels. In the novel, this is done via suicide attack (that forces them to revert to true form) and subsequently Ares shock troopers, but there are obviously other ways. Lynx appears here, but as an agent of the opposition and not as Lynx but a Mantid in disguise. Again, the player needs to be cooperative.
Follow that with a new character for Lynx' player (stocked up with money and Karma earned by Lynx through her short life, and topped off with a big bonus for playing along) and a one-shot to reacquanit PCs with Lynx II.
2. Module: EuphoriaPlay this straight out the box. The PCs re-encounter the spectral horrors that took Lynx! What ARE these beasts? Also, yes,
Amber Gel is Slurm.
3. Module: 2XS. One PC suddenly finds himself confronted by a minot Trid celebrity with a gun who accuses him of murdering her sister (character can be either gender; i'll use the masculine because in 2XS, that is Derek Montgomery). Turns out the PC had an affair with said sister (or brother, depending on preferences) and "proof" has been planted fingerhing him the murderer. Luckily, his Telecom has a saved message from that same sister/brother asking him for help, which defuses the confrontation. The PC in question should ideally be the face, not the super shooty fighter, obvs.
At the same time, the junkie sibling of another PC disappears.m Investigation reveals she was checked into a neighbourhood clinic in Puyallup (I'd not make this Brotherhood for flow reasons, but some church thing that has been infiltrated and funnels bodies to the Brotherhood hive in the SIPSES facility). Also, the gangers/chummers of junkie sibling accuse the PC of murdering their buddy who dropped sibling at the church, because chummer has by now been found in a dumpster, badly mauled. there character here ideally IS the super shooty fighter type.
Following up on the confrontation and an attempt on the Trid starlet (who hosts a show on paranormal critters on KTXX) and the disappeared sibling, traces show both being connected to SPISES. Ex-SO sibling overgheared something s/he should not regarding SPISES, and junkie sibling was funneled via CrashCart to a facility of Yamatetsu's in Fort Lewis, where something called SPISES is developed (which one day will come to be known as Move By Wire cybertechnology). Also, junkie sibling was on some new shit called 2XS, which seems to originate with the same facility, and is involved n a number of disappearances and a very public breakdown of another Trideo personality, a popular NewsNet anchor, all seemingly connected to CrashCart. During these investigations, they can already meet Patrick Bramba, the johnson in Bug City, and find out more about the insectoid threat. Also, a bunch of bugs attack them all of a sudden, just materializing out of thin air. Now they got their attention! The bugs were accompanied by a bug shaman whose foci are the same kind of revolting otherworldly as those from the guy who wanted to do ... stuff ... with euphoria and thise Slurm-producing abomination mutants!
They now need to infiltrate the SPISES facility, and liberate junkie sibling. they obviously need help, so hopefully they contact Karen King (if not, maybe she contacts them). King can hook them up with the top Yamatetsu guy, Jaques BArnard, who is uaware of anything untoward happening in his SPISES facility but is a bit pissed it is gaining so much attention. In the end, he consents to a probing operation, and off the mission goes.
This is the first boss fight. The PCs need to liberate incubating hosts '(including junkie sibling) and fight a boss fight with the bug queen, a bug shaman and a LOT of bugs.
Module 4: Universal BrotherhoodI'd play this fairly straight too. The players know a lot of the secrets already, but this will show them the true scale of the bugs' operation, and also burn a good deal of contacts of them if you played the Brotherhood as runners' helpers. Drop info on Project Hope and create an air of urgency about a possible army of thousands of bugs created from squatters.
Module 5: Double ExposureThe Johnson here should be King, assuming the runners tap Ares for help with the looming threat. King wants intel first and will not stand for carpet bombing charitable resocialisation projects just on a whim, because she'S old-fashioned like that. So in the runners go, up the bugs they scare, and down the hammer comes. Wham. Drop hints about a similar operation in chicago.
module 6: Bug City/Burning BrightHave the runners go to Chicago, maybe on Ares' ticket, maybe have King tell them off, whatever works. Have them trace the big nest, find it (they're bug experts now) and call it in.
Then the badly mishandled mission from Burning Bright happens. the hive erupts. Chaos and mayhem. The Ares raid is a desaster. Bug apocalypse! The runners have only one chance: detonate the nuke. They go in, someone sacrifices themselves (maybe Lynx II?) and boom it goes.
And then they have to survive Bug City.
This'll be a long campaign, for sure, and it needs players not too familiar with the background ideally. Also, it excludes SRR, because the overlap with UB there is just too great.