Yes, Nokia 8 does have a hybrid sim slot. You can use either 2 sim cards or 1 sim card & 1 MicroSD card.
Yes, Nokia 8 does have Always On display.
Yes, Nokia 8 does have an OTG support as well.
No. Technically, Nokia 8 is not a 100% water-resistant but it has got IP54 certification. That means that the phone can withstand minor water splashes.
It’s safe to say that if a smartphone like this had shipped from the Nokia stable a few years ago, the Finnish company might never have had to step back from the mobile business.