re: adventures:
- I've not played Splintered States, but my understanding is that it forces a couple of combat scenes early on that can be quite deadly to groups not used to the potential lethality of SR combat rules.
- Serrated Edge has a mix of freeform for data-gathering and infiltration, with some forced combat scenes. If they have enough hacking or social infiltration it might work well for them (there are multiple portions that occur in a large medical clinic, where they have to accomplish various goals without being obvious about it). One good thing about it for your group is that no part of really depends on magic.
- Converting 4th to 5th isn't too bad, especially for early adventures. 4th capped skills at 6, and used a different matrix and hacking system, but it was broadly similar. You might have to do a bit of fudging to get the challenge level right, but you'll have to fudge pretty much any SR adventure a bit in that regard, to meet your specific group. If you follow through that arc (the next one is False Flag, and the final is Ripping Reality), there is eventually some dragon interaction, but it may or may not be what you want.
- The missions tend to loosely tell a story each season, but you may find it pretty basic for a home campaign. But the Chicago seasons (all that are published for SR5) may not translate so well to other cities, due to the particular history of Chicago (the core was severely infested with bug spirits and got quarantined, they dropped a tactical nuke on the biggest(?) nest and dumped magic eating bacteria over most of the rest of the quarantine zone, and kept it isolated for some years and then restricted the movement in and out for until recently in the timeline)
- Season 1 and 2 of missions are available free on-line. They were published for SR3, which was quite a different rules system, but you can mine story ideas from them fairly easily. One particular one pops to mind, season 1, I think it was mission 2 or 3, called something like force reconnaissance. Basically the group is hired to gather intel on the layout and defenses of a new facility that has almost finished being built but isn't being used yet. It is a good opportunity for the group as a whole to get a handle on how the non-combat side of things work, are their dice pools good enough, etc. You'll have to adjust stats, but you can mostly just use appropriate professional rating goons from the SR5 core rule book, and put in a basic host of a reasonable rating for what the facility is.
I hope that is of some help.