FWIW I've slipped between my 16PM and ZF6 a few times (alongside my AWU2 and Galaxy Watch Ultra)
Both superb set ups and if you have a hand in both iOS and Android, easy to get on with / manage etc
The SGWU is a superb watch, it's not as well built / premium as the AWU2 but it's still really nicely made and feels great. Very easy to use and set up, but it's level of apps aren't as good as Apple, but still good, if that makes sense?
Both phones are excellent also and I never had any issues with the ZF6 - for me it takes great pictures, feels great in the hands and has superb functionality. And even with shovel like hands I had no issues with the front screen for the likes of messages etc (I use SwiftKey so being able to customise and expand then keyboard etc really helps); and that inner screen is just superb 👌🏼
Re S Pen, never used it. Never did on my previous Notes so never missed it.
Cases - I always ran rugged cases with spine protection, so stuck with Spigen Slim Armor. But their Aramod case is really good too and it looks like they're making all their ZF7 cases Magsafe too which is superb, as if fit the Spigen Magsafe adapters to the cases otherwise
Re earphones - they're Bluetooth so won't be any issues there I don't think. I use Earfun pods personally
Hope that helps