Hey there Mreiric66!
Samsung Pay is pretty good - I've just switched from Google Pay because I brought a Galaxy Watch Active2. It's not as straightforward to pay using your phone, but it prevents other people from just dumping your phone on a reader to pay for stuff.
In terms of putting Google Pay on Samsung's watches, they probably won't because Google Pay's designed for Android/Wear OS and Samsung's watches use Tizen - Google probably wouldn't write an app if Samsung asked them because it's a competing (and IMHO, better) platform to WearOS.
Hope this helps, and best wishes,
Tom 🙂