@Class73Electro Apologies for not closing the loop on this, I only had my work devices on this trip and could not log in here!
Basically, I registered my trip on the Entry to Europe app. I was in business and was one of the first to arrive at passport control on a sunday afternoon. The app doesn't seem to make any of the process easier, but the woman who served me said she could see my return ticket, and asked me what hotel I was staying at. She did not do the usual Swedish delay nonsense of asking to see hotel bookings or return flight but I noticed people who didn't use the Travel to Europe app did get harassed for this. You have to scan your right hand and selfie on entry.
On departure from Arlanda, they made me scan the fingerprints again and the selfie. Fortunately the queue was quite small but this feels like something that could go badly wrong if it was busy.
In summary, the worst of all worlds - register these biometrics, and have to talk to one of their useless passport officers - I've been in developing countries that do this better...