I just went to my phone's Galaxy Wearables app, Settings, Notifications.
Turn on the switch for Outlook, send yourself an email.
Works fine, did not install any extra apps on either device, or do anything to link anything up outside of the above.
There is a lot more apps in there I can link up as well, a golf game, JIRA, etc.
S9+ and Galaxy Watch (4) Bluetooth.
I loaded Microsoft Flow onto my laptop...and did a search for "sync outlook calendar to google calendar" followed the instructions. FLOW needed me to identify the calendars as it stepped through the instrucitons...cut once I selected the correct calendars and tested it...now it pushes changes to my Outlook calendar to my gmail account and calendar.
I am getting notifications on my Galaxy Watch like a playa...
Another solution that worked for me.
Have your gmail account linked to your samsung so it shows up under the default Calendar app.
Then have your Google account subscribe to your Outlook calendar: